Safe Food

Want to know more about the origin of Shigatoxin-producing E. coli?

2012-01-24T12:53:00.000-08:00

Bill Marler is a very rare individual: he is a lawyer with an ability to grasp the principles of microbiological food safety and to write about them in a way that is accessible to the general public. Bill has been closely involved in food borne illness litigation since 1993, when he obtained a $15.6 million settlement for Brianne Kiner, a nine year old girl who suffered HUS and ultimately kidney, liver and pancreas failure after eating Jack-in-the-Box hamburger. He has become a fiercely active food safety campaigner.

Recently, Bill conducted a literature review on the origins of Shigatoxin-producing Escherichia coli and has published the first two parts on his food safety blog. These publications are well worth reading - they are not written in highly technical language, but the reference list allows those readers sufficiently interested and capable to follow up his sources and read the original material.

Links to the first two parts are shown below:

http://www.marlerblog.com/lawyer-oped/where-the-hell-did-shiga-toxin-e-coli-come-from-a-literature-review---part-1/

http://www.marlerblog.com/case-news/where-the-hell-did-shiga-toxin-e-coli-come-from-a-literature-review---part-2/

There is just one problem with this review; Bill has taken away my option to set such a study of literature as an assignment for my postgraduate students in my course "Frontiers of Food Microbiology". The students will still be expected to read and discuss the material, but I can't use their reviews for assessment purposes. Thanks Bill!

Who ya gonna call - Ghost Busters?

2012-01-21T22:12:00.000-08:00

The title is perhaps a bit over the top for a food safety blog, but there is a link! Last week I spent a lot of time in my car and listened to many old tapes, including the theme song from Ghost Busters. According to my stats over the past week, a popular search phrase has been "Polysaccharide slime". It seemed propitious to write a short article on bacterial slime.

Bacterial biofilms produce large amounts of polysaccharide. Polysaccharides are chains of simple sugar molecules. Some polysaccharides are tough and fibrous but others can be slimy.

Bacteria growing in suspension, the so-called planktonic phase, generally don't produce large amounts of slime. However, for most bacteria, the normal mode of growth is as a biofilm - an aggregation of cells attached to and growing at a solid-liquid interface. It has been estimated that when the cells settle on the surface, up to 30% of the genome is switched on or off; the biofilm mode of growth is very different from the planktonic mode.

Among the changes is the production of large amounts of extracellular polymeric substance (EPS) much of which is polysaccharide. The EPS glues the cells to the surface and protects them from materials such as detergents, sanitisers and antibiotics. It also confers some advantages, such as immobilising extracellular enzymes.

In the food industry, we see EPS helping biofilms to remain in processing plant during cleaning, or bacteria spoiling foods such as meats by producing surface slime. However, not all slime is involved in food spoilage - dextran, produced by Leuconostoc mesenteroides and Streptococcus mutans and some other bacteria has laboratory and medical applications and may be used in construction of biosensors.

Moulds and mycotoxins

2012-01-09T09:58:00.000-08:00

Pepin Heights Orchards and Minnesota Department of Agriculture have issued advice to consumers not to drink certain batches of Honeycrisp Apple Cider because of the presence of patulin at levels slightly above the 50 microgram per litre maximum level recommended by the World health Organisation. See: http://www.prweb.com/releases/2012/1/prweb9085429.htm

Patulin is one of a host of compounds produced by moulds. These compounds are collectively referred to as "Mycotoxins".

We don't hear a lot about mycotoxins in the popular press - outbreaks of food borne illness are usually caused by Salmonella, Listeria, Campylobacter, or Escherichia coli, with several other bit players.

In fact, many fungi produce mycotoxins. One of my older textbooks devotes 66 pages of its 750 to these chemicals, some of which are very complex molecules. There is considerable discussion as to why moulds produce them, but they are probably just by-products of metabolism, though it has been suggested that in some cases, excretion of these "secondary metabolites" may confer some selective advantage, perhaps by inhibiting competitors in the soil.

Some of these chemicals can be very toxic - I well remember 1960 as the year when it was not possible to buy a turkey for Christmas in the UK, because thousands of young turkeys on poulry farms had died of the mysterious "Turkey X Disease". This was later shown to be caused by Aflatoxin present in peanut meal from Brazil as a result of growth of Aspergillus flavus mould. Intoxication of both humans and animals may be acute, but long term exposure may lead to cancer development.

Patulin in not regarded as particularly toxic to humans, but its presence in apple products is an indication of the quality of the apples used to make the products. There is some inconclusive evidence that patulin is genotoxic, i.e. it can damage the cell's genetic material. Pepin Heights has therefore been very responsible in their actions.

In America, fresh pressed apple juice is called Cider. In Europe, Cider, or Cidre is fermented apple juice. Patulin does not survive the fermentation process, so fermented cider is not likely to be contaminated with patulin.

Odd spot: a numbeer of mycotoxins are beneficial to humans, as they are in fact antibiotics - penicillin is just one example. Many drugs have also been made from mycotoxins.
St Anthony's Fire - ergot poisoning, has been known since about 600 BCE, but the pure ergotamine can be used to treat migraine.

For a much more complete, but readable, description of mycotoxins, go to: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC164220/

Is there such a thing as totally safe food?

2011-12-10T16:45:00.001-08:00

The short answer is "No!". Even if we eat only sterilised food, such as canned meat, we are reliant on the proper delivery of the sterilisation process and prevention of post-process contamination. Low acid canned foods are essentially sterile - the food is hermetically sealed in a can, which is then processed under pressure to destroy bacterial spores, specifically, the process is designed to reduce the chance of survival of a Clostridium botulinum spore to less than 1 in 10^12. On that basis, you have a better chance of winning the PowerBall lottery than getting botulism.

But nobody wants to live exclusively on canned food. Are there any other ways that we can make food safe, or at least reduce the risks of food poisoning to acceptable levels?

Yes! Food microbiologists and food processors study the bacteria that can cause food poisoning - pH range for growth, water activity range for growth, requirement for oxygen, growth temperature range, response to preservatives etc. - and they also look at the intrinsic parameters of the food - pH, water activity - and then consider the storage conditions, such as relative humidity, temperature and atmosphere in the pack etc.

Taking all these factors into account, foods can be designed to be safe under proper conditions of handling and storage. A significant part of the training of food technologists centres around study of these conditions and manipulation of the conditions in the food to achieve the manufacture of safe foods.

As an example, look at a tank of raw milk on the farm. Immediately after it is drawn from the cow, the milk is chilled. This reduces the growth rate of bacteria, which come either from the cow or the equipment. When the milk arrives at the processing factory, it is pasteurised - the temperature is raised to 72C and held for 15 seconds. This kills all the vegetative pathogens, that is, the bacteria that are not in the spore form. The milk is now safe, but will not keep indefinitely, because heat resistant spoilage bacteria are still present. We can make the milk keep for a much longer time by ultra high temperature processing (UHT). In this process, the milk is heated to around 140C and held for a few seconds. This sterilises the milk, so there are no viable bacteria to cause food poisoning or spoilage.

The milk can be dried to powder. This lowers its water activity below the threshold for bacterial or mould growth. Alternatively, the milk can be fermented to yoghurt or cheese by addition of starter cultures. The starters convert lactose to lactic acid and reduce the pH of the milk until it curdles and sets. pH is a measure of the acidity of the food; the scale runs from 0 to 14. Numbers below 7 are acid, those above are alkaline. As the pH falls, fewer and fewer bacteria are able to grow. Below pH 4.0 no pathogens are able to grow. Typical pH of yoghurt is 3.65 to 4.40

Other foods may be made safer by the application of hurdle technology, where several preservation mechanisms are brought together to prevent growth of pathogens in the food. There is a number of new technologies appearing, such as high pressure processing, electron beam irradiation and ohmic heating. None of these processes can guarantee safe food, but each has its advantages. I'll look at some of these techniques in future postings.

Safety management systems, like HACCP can be used to control food processing operations to ensure that safe food is produced. However, some foods are inherently less safe, such as raw vegetable sprouts, raw shellfish, or very unusual foods that require highly skilled preparation, such as fugu.

Consumers must take some responsibility in their choice of food and eating habits. If you are doing the traditional turkey for Christmas dinner, ensure that it is properly cooked - use a meat thermometer - and consider cooking the stuffing separately.

If you are going to barbecue this Christmas, don't cook chicken legs on the BBQ without first microwaving them - they are an irregular shape and ensuring that they are properly cooked is difficult. Don't use the same plate or utensils for cooked meat as for raw. Don't keep foods beyond their use-by date and ensure that all raw foods are refrigerated during storage.

Have a wonderful holiday and keep safe this Christmas.

It's the pits - bacterial hideaways

2011-12-09T21:27:00.000-08:00

Modern food processing is often carried out in stainless steel equipment - tanks, pipes, valves and conveyors are commonly made of various grades of stainless steel. We tend to think of "stainless" as not suffering from corrosion. To a large extent, this is true. Stainless steel has a natural oxide coating that prevents water molecules from oxidising the iron.

However, stainless steel can still corrode where grain boundaries or embedded contaminants allow water to access the iron. The contaminants might be grinding swarf from welding or repairs. Stainless steels may therefore benefit from a process called passivation, in which the surface is cleaned with sodium hydroxide and then treated with nitric acid. This restores the oxide film.

We use stainless steel in our laboratory experiments and routinely passivate with hot nitric acid. One of my students used a bottle labelled "Concentrated nitric acid" from the chemistry laboratory to passivate some new samples. Unfortunately, it appears that the contents were actually Aqua Regia, a mixture of nitric and hydrochloric acids. (How often have I said that correct labelling is critical in food safety?).

Chlorine ions are extremely electronegative and react strongly with certain compounds. They can severely damage stainless steel.

The first photograph shows two coupons treated with the acid mixture. It is obvious, even to the unaided eye, that the surface is pitted. Chloride pitting tends to occur at right angles to the surface, so deep pits form rapidly. Obviously, the use of aqua regia is a very extreme case of chloride attack, but even food materials containing sodium chloride will eventually attack stainless steel. Even 316 stainless steel, which contains molybdenum that helps to stabilise the passive film, will corrode if exposed to high levels of chloride ion, or if the oxygen level is very low. This is what may happen under a biofilm, where the bacteria use up the oxygen. The area then becomes anodic and current flows, resulting in corrosion and the formation of a pit.

I took a couple of coupons to Dr. Jen Wilkinson who runs our Scanning Electron Microscope. She took the following images, which show clearly the damage to the surface and the deep pits caused by the corrosion. The second image below shows the interior of the pit. Bacteria could easily enter the pit and would be very difficult to remove during cleaning. If the bacteria form a biofilm, they will be protected by the extracellular polymeric substances (EPS) which glue them to the surface and may inactivate disinfectants. The bacteria will be impossible to remove.

More on antibiotic use in animal rearing

2011-12-07T16:39:00.000-08:00

I wrote last month, suggesting that it is high time we banned the sub-therapeutic use of antibiotics currently used in human therapy for animal rearing.

When I wrote the article, I was not aware that the Food and Drug Administration had, around 9th November 2011, rejected two petitions to ban antibiotics from being used in food animal production. The petitions were filed by a coalition that included the American Public Health Association and the Union of Concerned Scientists.

It is troubling that in its denial letter, the FDA acknowledged that its “experience with contested, formal withdrawal proceedings is that the process can consume extensive periods of time and agency resources.” I interpret that to mean that FDA may well think that antibiotic use should be banned, but it can't afford to force the issue.

Meanwhile, researchers at McGill University have shown that bacteria resistant to tetracycline and tylosin can be isolated from pigs raised in a swine complex 2.5 years after administration of these antibiotics ceased. See Microbial Ecology DOI 10.1007/s00248-011-9954-0 published on-line 14th October 2011. Antibiotic resistance genes were found in the bacteria, though the workers were not able to explain their persistence long after antibiotic use ceased. The results are of significance for both animal and public health because these antibiotic resistant bacteria can be transferred between animals, humans and the environment.

Don't always blame the chicken - it spoils my sleep

2011-12-02T19:18:00.000-08:00

"The human understanding when it has once adopted an opinion ... draws all things else to support and agree with it. And though there be a greater number and weight of instances to be found on the other side, yet these it either neglects or despises, or else by some distinction sets aside or rejects". Francis Bacon, 1620.

A few years ago, I was flying from Hong Kong to Auckland. I sat with two attractive young women and enjoyed a glass of champagne with them before dinner. After the meal and film, the girls went off to spend time with other members of their party and I settled down for a sleep.

Some time during the flight, the cabin attendant shook me awake: "Dr. Brooks. Are you a real doctor?". Suppressing the urge to take him by the throat and educate him about academic qualifications, I asked what was the problem. It seemed that one of the girls and two others of their party had been taken seriously ill, and the attendant wanted me to open the airliner's medical pack to use the rehydration fluids for the victims. I explained that I was not qualified to do this and headed off to the galley to chat to the stewardess and persuade her I was really in need of a beer and some sandwiches.

Some time later, the girl who was not ill told me that her friends were vomitting and had diarrhoea. "It was the chicken pizza we had in the lounge before we boarded". The timing and symptoms didn't seem right to me and I asked a few questions, including what they had been doing in China. "Oh, we've been at a furniture expo for the last week". It didn't seem to occur to her that she had been snacking on canapes and eating buffet-style meals for the previous seven days; she immediately blamed the chicken. When we landed, her friends were taken by ambulance to the hospital, suffering from severe dehydration. I never heard from them again, but my money is on the meals during the week, not the chicken.

Now whenever I fly international, I ensure that my ticket is booked in the name "Professor Brooks". I'm more likely to get a decent sleep during the flight.

Your all-time favourites

2011-12-02T12:55:00.000-08:00

I have just reviewed the most common search terms resulting in visits to this blog.

By far the most common has been "Coliforms in food". This has been a regular search since I started writing Safe Food in 2006, but has perhaps appeared more frequently since the Escherichia coli O104:H4 outbreak in Europe.

Coliforms are used as "indicator organisms" to show whether the food has been processed under hygienic conditions. Presence of these bacteria mean that the food has potentially been contaminated with faecal material and hence faecal organisms, but to confirm this, we look for Escherichia coli presence in the food.

Surprisingly, the next most common search has been "Safety of Probiotics". Probiotic bacteria are those that confer some benefit on the host. Thus many foods, such as yoghurt, contain live bacteria that may colonise the gut of the consumer and confer some benefit. These bacteria are often lactic acid bacteria. Many claims have been made for the benefits of consumption, though there are some indications that administration to critically ill patients with acute pancreatitis may have deleterious effects. There is also some evidence that administration to infants under 6 months of age may render them more prone to development of sensitivity to allergens. For the majority of consumers, however, probiotics will not be hazardous and may be beneficial.

Do not confuse probiotics with "prebiotics". These were so named by Marcel Roberfroid in 1995, who later wrote the definition: "A prebiotic is a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confers benefits upon host well-being and health." A major class of prebiotic is soluble fibre.

Much lower down the list are "Listeria in vegetables" and "Safety of chicken". There has been a small spike in Listeria searches, probably as a result of recent recalls and the cantaloupe outbreak in USA that has killed approximately 29 people. The incidence of listeriosis is very low and victims are usually neonates, the elderly and those people with compromised immune systems, but this outbreak seems to have been particularly dangerous. Chicken has made regular appearances in the news, either being a vehicle for Salmonella or Campylobacter. The incidence of Campylobacter infections in New Zealand has dropped significantly since the introduction of more stringent controls and biosecurity systems.

One new search now appearing is a bit disturbing: "Will eating spoiled food make you sick?". I have previously written on this after receiving a direct question from a reader. Is the increased interest a result of hardship in the community, or merely a thirst for knowledge? I hope it is the latter.

Time to ban antibiotic use in animal husbandry?

2011-11-14T12:32:00.000-08:00

As a microbiologist, I sometimes worry that we are killing the golden goose in terms of our ability to combat human disease. As I wrote earlier, the cost of developing and bringing to market new drugs is astronomical and many companies are shunning new drug development in favour of more lucrative endeavours, such as development of molecular-based test kits for human disease diagnosis.

In this light, it is disturbing to read of the amount of antibiotics used in animal production. In 2001, Kristin Leutwyler wrote in Scientific American that a study by the Union for Concerned
Scientists had shown meat producers in the USA feed around 25 million pounds of antibiotics to chickens, pigs and cows for non-therapeutic purposes each year (the antibiotics suppress microbial populations and lead to increased growth rates of the animals). Compared with this, only 3 million pounds per year are used for treating human disease.

In 2009, the House Committee on Rules held a hearing: H.R. 1549 - Preservation of Antibiotics for Medical Treatment Act of 2009, which would have amended the Federal Food, Drug, and Cosmetic Act to require the Secretary of Health and Human Services to deny an application for a new animal drug that is a "critical antimicrobial animal drug" (CAAD) unless the applicant demonstrated a reasonable certainty of no harm to human health due to the development of antimicrobial resistance attributable to the non-therapeutic use of the drug.

The CAAD is a drug intended for use in food-producing animals that contains specified antibiotics, or other drugs used in humans to treat or prevent disease or infection caused by microorganisms. The Rule would also require the Secretary to withdraw approval of a non-therapeutic use of such drugs in food-producing animals two years after the date of enactment of the Act unless certain safety requirements are met.

That rule died in Committee. It has been reintroduced in the 2011-2012 Congress, and went to Committee on 9th March, 2011.

It has been argued that there are no good studies linking antibiotic use in animal rearing to the development of antibiotic-resistant diseases.

While this may be so, and I'm not sure that it is, it is hard to imagine how else multiple antibiotic resistant strains of bacteria could be found in animals and ultimately in humans. A classic experiment shown to most undergraduate students of microbiology over the last 50 years is the selection of antibiotic-resistant bacteria. All that is required is the production of a concentration gradient of antibiotic across a Petri dish. The agar is seeded with the target bacteria and those that grow at the most concentrated side are picked off and recultured on another gradient. Very quickly, a resistant strain can be isolated.

This laboratory procedure is effectively repeated in animals fed sub-therapeutic levels of antibiotics in their diet or drinking water - the survivors of the first dose are constantly exposed and eventually dominate the population. As microorganisms transfer genetic information among themselves, the number of different strains resistant to the antibiotics also increases.

I would be less concerned if the antibiotics used for treating animals were no longer in use for human therapy. Then the benefits could perhaps be justified, though even then, the class of antibiotic is important, as bacteria becoming resistant to one member of the class might also develop resistance to others. If humans become infected by strains resistant to antibiotics used in human therapy, there may be no cure available for the infection. These infections could easily be transferred by handling raw meats from treated animals, though there is again a lack of sound scientific evidence.

The view is clouded by the indiscriminate use of antibiotics by humans. It's not just a case of doctors prescribing antibiotics when they are not justified, though I have seen antibiotics prescribed for viral diseases, which generally can't be treated with these chemicals. Look up "availability of antibiotics over the counter" and you will get pages telling you that there is none. However, it is well known that antibiotics can be bought freely over the counter in some countries. Even the antibiotics of last resort - the only ones that can treat certain diseases - can be bought in pharmacies in some Asian countries and there are papers in the scientific literature showing the levels of resistance in bacterial populations.

I truly hope that President Obama eventually signs this legislation and that leaders of other countries do likewise. I would hate for us to descend to the state before the introduction of penicillin, when even a scratch from a rose thorn could result in painful death.

Those dreadful scientists - do they ever do any good?

2011-11-08T01:33:00.000-08:00

If you read the popular press, you could be excused for thinking that scientists, particularly the genetic engineers, are a pretty bad bunch. Wandering round spooky laboratories wearing white coats, these bearded boffins invented preservatives that are now widely used in processed foods, they developed milk pasteurisation and homogenisation, and the genetic engineers made corn with built-in insecticide. Food technologists are employed by food manufacturers to make food keep forever and fool the consumers.

My perhaps somewhat biased view is that this is absolute rubbish. To name just a few good things, we have safe food and effective vaccines, a whole range of new fruit cultivars and wonderful test kits that can quickly diagnose all kinds of disease. All these things were developed by scientists, technologists and engineers.

A recent report from Cornell University describes a new test to trace and identify outbreaks of foodborne disease. So far this is applied only to a common Salmonella subspecies, but the principle can be applied to many other foodborne disease bacteria.

One way of recognising a specific bacterial strain, such as one suspected of causing a food poisoning outbreak, is to chop up the DNA into bits with enzymes and to amplify the bits, followed by separation of the fragments by gel electrophoresis, which is a way of creating a band pattern or fingerprint. Alternatively, parts of the DNA can be amplified with random primers, or starting sequences, that will also produce a fingerprint. You will have seen DNA fingerprints used for crime detection in various television series. However, it is never as quick and simple as portrayed in these cop shows. Unfortunately, closely related bacteria may produce band patterns that can't be distinguished, making it impossible to differentiate one strain from another.

With the development of very rapid sequencing techniques, it is now possible to determine the nucleotide sequence of the full bacterial genome. In other words, we can read the whole genetic code of the bacterium. Very closely related strains may differ by only a few nucleotides, or code letters. By looking at these very small differences, we can tell if a particular strain was responsible for apparently linked illnesses in Germany, United Kingdom, New York, and France. The technique is called Single Nucleotide Polymorphism (SNP) test.

The technique is still quite expensive, but as rapid sequencing is developed further, the cost is likely to decrease. Being able to track an infecting bacterium, such as the Escherichia coli that caused so much disease and death in Europe earlier this year, is a valuable tool in fighting such outbreaks. In the face of such devastating outbreaks of foodborne disease, the cost of full sequencing is insignificant.

The researchers, led by Martin Wiedmann, who developed the technique intend to continue perfecting the method and to apply it to other bacteria.

Of course, the description above is a gross simplification of the SNP test. Wiedmann's original paper is highly technical. You can read it in:
Applied and Environmental Microbiology, 2011; DOI: 10.1128/AEM.06538-11

Alternatively, you can read a press release from Cornell University at:
http://www.sciencedaily.com/releases/2011/10/111025113540.htm#.TqoxsV5BB1U.email

Food Safe Families: Does it Prevent Contamination of Foods? Guest Editorial

2011-10-11T16:05:00.000-07:00

Patricia Walling^*

In just about any news medium, headlines about recalls of meat, poultry and produce due to contamination occur with deadly regularity. Sadly as anyone in health care (from those in medical billing and coding to nursing) knows these headlines aren't just hype; food borne diseases can be fatal. This is especially true when they infect the very young, elderly and those with compromised immune systems.

According to the Center for Disease Control and Prevention (CDC) “each year, 1 in 6 Americans, or 48 million people get sick, 128,000 are hospitalized and 3,000 die of food borne diseases.” The agency notes that among the 31 known food borne pathogens, the leading causes of deaths and hospitalization are: Salmonella, Toxoplasma, Listeria, norovirus and Campylobacter.

Based on this public health problem, a partnership was formed among several U.S. governmental agencies (including the U.S. Department of Agriculture, the Department of Health and Human Services, the Food Safety and Inspection Service, Food and Drug Administration and the CDC) that are charged with keeping the food sources safe in conjunction with the Ad Council. The campaign, recently announced by the USDA, is titled “Food Safe Families.”

These organizations feel that this promotional effort will “shift the way people think about food handling so they can take a more proactive approach at home to help reduce food-related illnesses.” However, not everyone feels this educational and health promotion campaign will do much to solve the real challenges of the food distribution system.

The Food Safe Families Program

Public service campaigns, created by U.S. governmental agencies have a storied history. From the iconic U.S. Forest Service and Ad Council campaign that featured Smokey Bear admonishing that: “Only you can prevent forest fires” (launched in 1947), to the FDA’s “Food Pyramid” (first launched in 1992, updated in 2005 and then replaced in 2011), there have been hundreds of public service campaigns that are well-meaning but often ineffective.

Will the Food Safe Families campaign have the promotional “legs” of Smokey Bear’s message or join “Just Say No” campaign as a waste of taxpayer money? Only time will tell. However, the campaign includes several aspects that make it important.

According to the USDA Food Blog, “using the motto “Check Your Steps,” Food Safe Families aims to get consumers to adopt four very easy steps when preparing food:

1. Clean: Clean kitchen surfaces, utensils and hands with soap and water when preparing food.

2. Separate: Separate raw meats from other foods by using different cutting boards.

3. Cook: Cook foods to the right temperature by using a food thermometer.

4. Chill: Chill raw and prepared foods promptly.”

These four steps – clean, separate, cook and chill – serve as the graphic and messaging platform of the campaign. The agencies hope that by constantly reiterating this message, it will become ingrained in those who are charged with preparing the family meals.

Even the timing of the launch was important. The agencies choose Jun. 28, 2011, because this is the start of summer and represents the prime outdoor grilling season for most families. The USDA noted in its blog that “food borne illnesses tend increase with more outdoor meals.”

Once the campaign was launched, it seemed that Food Safe Families had covered most of the promotional bases. There were spiffy new graphics, memorable message points, an innovative social media campaign and public service media all up and running. The timing and execution of the campaign was excellent, until people started showing up in emergency rooms with symptoms of Listeriosis.

The Listeria Outbreak

Jensen Farms, located in Holly, Colorado grows and ships cantaloupes throughout the United States. After numerous reports of an outbreak of Listeriosis, the FDA and CDC traced the contaminated melons back to this farm. According to a news update from the FDA on Sept. 30, 2011, “the cantaloupes were produced from the end of July to Sept. 10, 2011. Given that the Jensen Farms’ recall has been in effect for more than two weeks, it is expected that all of the recalled whole Jensen Farms cantaloupes have been removed from the marketplace.”

The website for the Mayo Clinic notes that “Listeria infection is a food-borne illness that can be very serious for pregnant women and people with impaired immune systems. Listeria bacteria can survive refrigeration and even freezing.” As of Oct. 1, 2011, the CDC reported that the contamination had been responsible for the deaths of 17 people and the illness of 84 across 19 states.

In response to this outbreak, the FDA noted that “It is very important that consumers clean their refrigerators and other food preparation surfaces. Consumers should follow these simple steps:

• Wash hands with warm water and soap for at least 20 seconds before and after handling food.

• Wash the inside walls and shelves of the refrigerator, as well as cutting boards and countertops.

• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.

• Always wash hands with warm water and soap following the cleaning and sanitization process.”

Do These Guidelines Prevent Food Borne Illness?

For all of the regulations, safeguards, inspections and, yes, public service campaigns, the growers and processors of food employ humans and sometimes they get careless and make mistakes. Such is also the case with homemakers.

In cases where these mistakes cause deadly diseases to spread, the Food Safe Families campaign could help to ameliorate the damages from contaminated cantaloupes, ground meat, peanut butter or any other food. However, it will have no effect on preventing the disease from starting. That involves many other factors. These include: the distance and the number of companies that must handle food between the farm and family and the quantity and quality of the inspections along the distribution channels.

Given time, the Food Safe Families campaign could have a positive impact on the health of U.S. citizens. Even now, the use of the social networks that were launched for this campaign have served as valuable tools to help with the dissemination of information about the latest contamination. However, such programs as buying foods that are produced closer to home may have more impact.

* Patricia Walling

Patricia Walling is a web content designer for several healthcare-related sites. She self-identifies as a perpetual student of medicine, and can be found most of the time researching anything
related to the field. She lives in Washington, and as a result loves the long winters.

Ten Biggest Food Recalls in US History - link

2011-10-05T14:13:00.000-07:00

I was recently contacted by a reader who included a link to a commercial website. I would not normally publish such a comment, but this site does contain useful information, primarily for American businesses.

The page she specifically included lists ten very large food recalls in the US. I'm not sure if they are listed in order of cost, volume of product or effect on consumers, and there is only minimal detail. However, I have included the link here so that interested readers may search further to obtain more detail on these recalls.

http://www.businessinsurance.org/10-biggest-food-recalls-in-u-s-history/

Cidre with that extra fizz could be a nasty surprise

2011-09-17T23:23:00.000-07:00

The UK Standards Agency announced on the 18th September that InBev was recalling three batch codes of Stella Artois Cidre in bottles. Fruit juices and alcoholic beverages make few appearances in lists of hazardous foods and drinks, and this is the first time they feature in Safe Food.

The problem with these batches is yeast. Yeast is used in bread making, beer fermentation and, of course, Vegemite, the breakfast spread many New Zealanders were brought up on. So why is yeast dangerous?

Yeasts convert sugar to alcohol and carbon dioxide. They put the fizz in beers and sparkling wines. If this occurs in a controlled fermentation process, there is no problem. However, if yeasts get into finished products containing sugar, such as bottled fruit juices or alcoholic beverages with residual sugar (not fermented to "dryness"), they can produce carbon dioxide in the bottle. The cells can generate pressures up to 10 atmospheres - sufficient to burst the bottle.

The recall notice says:

handle the bottles carefully, wearing gloves and protective eyewear, to determine if the product is from the affected batch
on an individual bottle, the batch code is printed on the bottle’s neck
on a 12-pack the batch code can be located on the long side of the pack, to the right of the barcode

If you do have a product from an affected batch, please call InBev as soon as possible on 0800 0731736 between 8am and 8pm. Do not consume or handle the product further.

I once saw a similar recall notice that effectively invited anyone having the affected product not to touch it, but to call the bomb squad!

This may sound a bit melodramatic, but think about this:
One of my winemaking colleagues wanted to produce sparkling wine from a batch of still wine. He calculated the amount of carbon dioxide to dissolve in the wine and added this to the bottles as small pellets of carbon dioxide ice. He put corks in the bottles and wired them on and then stored the bottles in a cupboard.

A few hours later, there was a tremendous bang from the cupboard. He found only the necks and bases of the bottles; the rest was fragments, many of them embedded in the wooden walls of the cupboard. We could only assume that the carbon dioxide had been slow to dissolve in the wine and the pressure had built up too fast. This could have been very nasty had he been holding a bottle at the time.

As they say in the extreme sports programmes, "Don't try this at home".

Big One becomes Big Seven

2011-09-14T19:20:00.000-07:00

Escherichia coli O157:H7 has now been joined on the FSIS most unwanted list by the "Big Six" - other strains of E. coli capable of producing Shigatoxin.

As we saw in May and June 2011 in the German outbreak, Shigatoxin-producing E. coli can cause a potentially deadly food borne infection that can leave survivors damaged for life. The outbreak also resulted in huge economic loss in several European countries as fresh produce was either banned by authorities or shunned by consumers.

As of the 13th September 2011, these seven strains - O157:H7, O26, O11, O103, O121, O45 and O145 - will not be permitted in non-intact raw beef in USA. If they are found to be present, the meat must either be destroyed or cooked before sale.

It has been a long road to get to this point. In October 2009, Bill Marler, a US attorney, filed a petition with USDA/FSIS for an Interpretive Rule declaring all enterohaemorrhagic Shigatoxin-producing serotypes of E. coli, including non-O157 serotypes, to be Adulterants within the meaning of the Federal Meat Inspection Act.

Not much has been heard since, though there has been a certain amount of correspondence. Even the regulatory authorities didn't seem to have a united view. On the 3rd June 2011, the Deputy Director of CFSAN, Donald Kraemer, stated on the FDA website "FDA considers any disease-causing strain of E. coli in food to be illegal”. The FSIS deems only O157:H7 to be an adulterant. Tellingly, Kraemer’s comment was removed from FDA website on 5th July 2011.

The new declaration is being hailed as a victory. Elisabeth Hagen, head of food safety at the Department of Agriculture, said that this was "one of the biggest steps forward in the protection of the beef supply in some time. We’re doing this to prevent illness and to save lives.” A worthy cause.

However, I have some concerns about this optimism. Will the reclassification of the Big Six make meat safer? I'm not so sure. Certainly, if these bacteria are detected in meat, the product will not be allowed on the market unless it is diverted to cooked products. This may be a challenge for the meat processors - since 1994, O157:H7 in raw ground beef has been declared an adulterant with zero tolerance by FSIS. In October 2007, the Topps Meat Company recalled 21.7 million pounds of ground beef, bringing the total recalls in the US between April and October 2007 to over 30 million pounds of red meat, mostly hamburger. A company manufacturing frozen hamburger patties is unlikely to have the capacity to redirect this much meat to a cooking process and there may be difficulties in finding a buyer for the product, so it may have to be destroyed.

Secondly, as far as I am aware, there is no requirement for processors to test for these bacteria. If this situation doesn't change, the first indication that something is wrong may still be when people start showing up at the hospital with gastrointestinal disease.

Thirdly, the cost of testing is currently very high and the testing may take up to 5 days, even when things go well. I have already written about the impossibility of guaranteeing safe food by testing.

Finally, testing for the Big Seven will miss any Shigatoxin-producing non-members, as was the case with the German outbreak of O104:H4

The FSIS move is a good start and is motivated by good reasons. However, the only way that safety of food can be improved is by development of risk management plans and rigorous application of critical control points throughout the food chain, including food service outlets, i.e. farm to fork. Consumers should not receive contaminated food, but they too must play their part by prevention of cross contamination in the home and proper cooking of foods. Future posts will deal with some of these approaches.

Where does that leave us with foods like sprouts? Food for thought.

Since I wrote this article, Shawn Stevens has written an article "Big six declared Adulterants: Is it a good thing?" in Meatingplace.com, a blog for the meat industry in the US. It seems that he too has some concerns. You may have to register to read the article, but registration is free.

"Safe Food" makes the top 50

2011-09-10T15:32:00.000-07:00

I recently received an e-mail from Paul Hench, who writes for http://www.mastersinpublichealth.net/, a website dedicated to providing students with the information and tools needed in order to pursue their Masters in Public Health.

Paul has included Safe Food in his top 50 list of food safety blogs. Though unofficial, this list puts Safe Food alongside blogs that I regard as important sources of information and opinion and it's gratifying to see this recognition. The list will be a valuable resource, not just for PH students, but for all those interested in food safety.

I have not yet searched the whole list and therefore cannot endorse these blogs, but you may care to check them out for yourself. Goto:

http://www.mastersinpublichealth.net/top-50-food-safety-blogs/

Natural mercury in fish

2011-08-24T15:01:00.000-07:00

Most of the posts on this blog are about bacterial food poisoning, so this post is a change on two counts.

Mercury contamination of fish is usually associated with industrial pollution of rivers and estuaries. William Ray, of Radio New Zealand, today reported that experts have suggested that the levels of mercury in trout in waterways around Totorua are so high, people should limit their intake to one trout per month. (I wish I could catch so many!).

Rotorua is one of New Zealand's most famous geothermal areas and the experts have suggested that the mercury is from natural hydrothermal sources. However, it appears that runoff from farms in the area may also be involved. The nutrients washed into the rivers and lakes cause algal blooms, which lower the dissolved oxygen content of the water. This in turn allows transfer of mercury from mud into the water, from whence it enters the food chain.

Perhaps the most infamous mercury poisoning occurred in the Japanese city of Minamata, which gave the name Chisso-Minamata disease to the resulting neurological syndrome. The Chisso Corporation chemical factory released methyl mercury into the Minamata Bay and this highly toxic compound was accumulated by fish and shellfish.

The Rotorua trout have also accumulated mercury, but Dr. Ngaire Phillips from the National Institute of Water and Atmospheric Research points out that the recommendation for consumption of no more than one trout per month is based on a lifetime consumption.

Listeria and bacon recall

2011-08-13T22:44:00.000-07:00

I was just scanning the news and did a double take. An Ontario company, Aliments Prince, S.E.C., has just recalled 380,000 lbs of bacon because of possible contamination with Listeria monocytogenes. That's a lot of bacon!

It seemed to me that this was excessively cautious. L. monocytogenes should not be found in a food product that has been processed in such a way that the bacteria should not survive, but the organism can occasionally be found in foods that have not been given a listericidal process. So green leafy vegetables and other raw foods may occasionally contain L. monocytogenes. The bacteria can be found in many parts of the environment, such as surface water, soil and decaying vegetation, and it's not surprising to find it turning up sometimes in raw foods.

On closer reading, it turns out that the FSIS found a sample of cooked diced bacon from Aliments Prince contained the bacteria. This is a whole new ball game - the product could be expected to be consumed without further heating and thus could put at risk susceptible consumers. See my post "Listeria Hysteria" for further information.

The company has done the right thing. We can't avoid occasional low levels of contamination of raw foods by L. monocytogenes, but something has gone seriously wrong when we find it in cooked foods. Either the process given was too mild, or, much more likely, the product has been recontaminated post processing.

Haemolytic Uraemic Syndrome

2011-08-09T15:12:00.000-07:00

In the wake of infection by Shigatoxin producing Escherichia coli (STEC), some patients develop Haemolytic Uraemic Syndrome (HUS). The recent outbreak of O104:H4 STEC in Europe resulted in an unusually high proportion of patients going on to develop the syndrome, some of whom succumbed to the infection.

Drew Falkenstein, an associate of Marler Clark law firm in Seattle, has written a very well informed article on HUS. Rather than write another, I suggest that interested readers follow the link to Drew's posting on Food Poison Journal.

Hello, how are you, is it seeds you're looking for?

2011-07-20T15:02:00.000-07:00

It's all over, bar the shouting. Or is it?

As at 30th June, 2011, there were 50 reported deaths from the Escherichia coli O104:H4 outbreak centred in Germany. Cases of illness have been reported from 16 countries, not all victims having travelled to Germany. This suggests that there may have been some person-to-person infection, though in at least one case, there appears to be none of these links.

Thankfully, the number of cases reported is dropping, the outbreak following a classic curve of increasing number of cases, followed by a decrease once reporting shows that there is an outbreak under way and information and preventative measures become available.

European scientists and government sources have suggested that fenugreek seeds imported from Egypt in either 2009 or 2010 are implicated in the outbreaks in Germany and Bordeaux. Epidemiological investigations do link these particular sprout seeds with the outbreaks. But a link is not proof.

Not surprisingly, the Egyptians have objected to their seeds being blamed for the outbreak. I have some sympathy with them - as far as I am aware, O104:H4 has not been isolated from any seed samples. If these seeds are the source, then we have another problem on our hands.

If the seeds were imported to Germany and France, and perhaps other countries, the implication is that any E. coli O104:H4 present in the seeds survived for between two and three years before the sprouting process allowed them to multiply and cause the outbreak. This raises a number of questions: is this strain of E. coli particularly hardy, so that it can survive for years in dry seeds? Were all the infected seeds exported from Egypt? If not, were there any O104:H4 cases in Egypt between 2009 and the present? If there were cases, why have we not heard about it?

I don't believe that we have heard the last of this by a long chalk.

Mud hoppers

2011-07-08T17:15:00.000-07:00

This post is not directly about food, but it is about eating stuff.

Over the last weekend, an annual event was run (well actually, quite a bit of it was crawled) over a 6km course in Auckland. Nothing unusual about cross country running in New Zealand, but this one involved obstacles to crawl under or climb over and a very large amount of mud. Two TV news presenters took part, so there was plenty of footage to analyse.

I am all for active sports, but I wonder how many of the competitors will regret the weekend's activities, and not just for sore muscles. At one point, the competitors crawled, sploshed or "swam" though a trench full of thick mud. At least one competitor dived headfirst into the mud as if he were diving into the surf. None of the participants could have avoided getting some of the mud in their mouths.

Soil is interesting stuff - it's the goto place for microbiologists if they need to isolate a microorganism that has a particular characteristic; it's one of the best sources of bacteria. If animals have been grazed on the paddock, or water in the mud has drained from a farm, it is likely that the mud will contain many faecal organisms. In 2008, there was a significant outbreak of campylobacteriosis after a mountain bike race, in which competitors got very muddy. None of the support crews became ill.

I'm sure that mud running allows us to relive our childhood without being scolded for getting dirty and it's certainly a good spectator sport, but competitors should be aware of the risks associated with eating the stuff.

Can we control toxigenic E. coli?

2011-07-02T22:23:00.000-07:00

Last week at the New Zealand Institute of Food Science and Technology annual conference, I presented a paper on non-O157:H7 shigatoxigenic E. coli. That's a bit of a mouthful, if you'll pardon the unfortunate pun. These bacteria have gained the ability to produce a toxin that can destroy intestinal epithelial cells and also damage the kidney. E. coli O157:H7 is probably the best known of the Enterohaemorrhagic E. coli (EHEC) types. The strain causing the outbreak in Germany and other parts of Europe is a non-O157 type and indeed appears to be from a different group - the Entero-Aggregtive EC.

During the session, two other papers were presented, one on Cronobacter sakazakii - the neonate nasty, and one on Salmonella. All three presenters talked about control of these food borne disease-causing organisms.

During the discussions, it became apparent that there was some difference of opinion on the effectiveness of control measures during production and processing of foods.

For example, the poultry industry in New Zealand has been remarkably successful in controlling Salmonella in poultry flocks by strict management of biosecurity, and thus eggs and chicken meat are essentially free of Salmonella. Unfortunately, these controls have not worked for Campylobacter and there is still a significant rate of C. jejuni illness that can be traced to poultry, though this rate has fallen over the past two years.

Similarly, when I suggested that control of Salmonella would likely also control E. coli, a friend and colleague stood up and said that these two organisms are significantly different and controls would need to be tailored to each. I invited him to come outside and we'd sort it out by fisticuffs! However, it became obvious that we were talking at cross purposes and we were both right.

Salmonella, Cronobacter and E. coli are all vegetative bacteria. That is, they do not form spores and are not particularly heat or chemical resistant. Thus, during food processing or in the hands of the consumer, control is easy - heating to about 75-80C for a few seconds will kill them all. If we prevent cross contamination, then the finished food will be safe to eat.

It is much more difficult to set conditions during primary production that will control these bacteria. Vegetables are usually grown in soil. They therefore become contaminated with soil organisms. Even hydroponic growing systems may become colonised by bacterial biofilms and thus contaminate the products. Animals and birds all carry populations of bacteria in their guts or on hides, hair, feathers and feet. It is impossible to eradicate these bacteria, so they must be controlled during processing.

But what do we do with vegetable sprouts? These products must be regarded as hazardous - they are grown in conditions of high humidity and at temperatures that support the rapid growth of bacteria. If pathogens, such as E. coli O104:H4 are present in the seeds, in the water or the equipment, they can grow rapidly. Stir-frying will probably kill the bacteria, provided the temperature gets high enough. Sprouts are also eaten raw, so there is no controlled lethal process step and the consumer ingests the bacteria, sometimes with fatal results. If people are to continue to eat raw sprouts, we need to develop some means of decontaminating them, such as a rinse in a bactericidal chemical solution. Nothing is perfect, but control of production, processing and distribution, together with consumer education, should decrease the likelihood of a similar outbreak to that currently occurring in Germany.

Gloves don't make you bombproof

2011-06-24T20:44:00.000-07:00

This week, my wife watched a professional catering company setting out a room for conference meals.

One of the girls was setting out plates with her bare hands. She then returned to the room with plastic wrapped bananas on a pile of plates. She was wearing one plastic glove and contrived to remove the plastic wrap from the bananas with the ungloved hand. She then carefully separated the individual bananas using the gloved hand.

What did this achieve? I don't have a major problem with the plates being set out with bare hands, provided she washed her hands before she started. The wrapped bananas were in contact with the plates, so anything on the plastic wrap might also be transferred to the plates. Unless the girl was a part-time juggler, it's likely that she touched the banana skins with her bare hand as well as with the gloved one. But people don't eat the skins and anyway, how many hands had touched the skins during harvesting and transport?

Many years ago, when I first started teaching food microbiology, O.P Snyder used to write regularly about the hazards associated with handling food with bare hands or with gloves. He argued that the use of clean hands was less hazardous than unchanged gloves. The critical words here are "clean hands".

There is no doubt that contamination can be transferred by manual handling of food. Some regulatory authorities require that food handlers wear gloves and do not permit contact between bare hands and ready-to-eat foods.

However, simple observation in kitchens and service areas show that many food handlers do not know how to use gloves to improve food safety. Chefs often use their fingers to assemble food; counter staff handle food while wearing gloves and then clean the counters before going back to handling food without changing the gloves. When gloves are changed, are the hands washed? Usually not, so hands that have become sweaty inside the gloves are then used to put on the fresh gloves and must inevitably transfer some bacteria to the new gloves.

Dirty gloves are just as dirty as dirty hands. Wearing gloves does not make you bombproof - you have to keep your brain engaged when handling food.

I look forward with interest to the discussion that this post is bound to generate.

For more information on gloves in food service, go to:
http://www.foodsmart.govt.nz/elibrary/myth_busting_about.htm

Colonel Mustard, in the Dining Room, with the Sprouts

2011-06-17T18:18:00.000-07:00

The last couple of weeks have been like the old game of Cluedo, with everyone running round accusing various participant of foul play and trying to find the culprit. It would be amusing if it were not so deadly serious.

It now appears that the outbreak of Escherichia coli O104:H4 in Germany, which has now reached 16 countries, was probably caused by fresh vegetable sprouts grown in a farm in Uelzen, near Hamburg. Unfortunately, cucumbers from Spain, lettuces and tomatoes also had the finger pointed almost indiscriminately at them. That caused huge financial losses for the suppliers and had knock-on effects on vegetable sales throughout Europe. In some ways, I can sympathise with the authorities and the media. This is one of the largest and most serious outbreaks of food poisoning ever and finding the source as quickly as possibly was imperative.

At the time of writing, there have been 3517 cases of EHEC infection, resulting in an unprecedented 839 cases of Haemolytic Uraemic Syndrome and 39 deaths. The rate of new case reporting has slowed, but it is likely that more people will become ill before this is all over.

This shows just how difficult it is to pinpoint the source of an outbreak of food poisoning in our highly integrated and widespread food supply chain. The sprout farm purchased seeds for sprouting from both European and Asian countries. The seeds were sprouted, using what seems to be standard and well designed conditions, and the 18 different sprout mixtures were sent to many different points in Germany.

The German authorities have been accused of being in disarray and having no proper response prepared. There may be some truth in this - if the responsibility for food safety is spread across many local authorities and agencies, setting up a coordinated and timely response is fraught with difficulty. But it is generally recognised that epidemiological investigations may have a success rate as low as 33% in tracking down the source of infections and the chance of success falls as time goes on.

At times like this, we often hear calls for increased testing of products before they are released onto the market. Good try, but no cigar! For a number of reasons, microbiological testing to assure safety of food is just not possible. Testing is expensive and time consuming. In some cases, the testing period exceeds the shelf life of the product. A simple statistical calculation shows that when contamination levels are low, the number of samples that must be tested to get even a 95% chance of detection is prohibitively large and even then, 5% of contaminated samples will be accepted as safe. Testing for E. coli O157:H7 would not have picked up the German strain and even proposed widened testing for "The Big Six" Entero-Haemorrhagic E. coli strains would have missed this one.

Regulators must be strong in the coming months. Microbiological testing gives only a retrospective view and a poor one at that. Imposing increased mandatory testing will not assure the safety of foods.

The only way we can ensure the safety of our food supply is to introduce controlled lethal steps in processing, such as heating or irradiation, or to put in place rigorous control of every potentially hazardous ingredient, process step, processing facility and distribution chain. This is particularly important with high risk products such as sprouts. What every food producer and distributor needs is a Hazard Analysis based Food Safety Programme of Risk Management.

Is it sprouts now?

2011-06-06T01:51:00.000-07:00

German authorities have now identified sprouts as the putative source of the outbreak of Escherichia coli O104:H4 food poisoning.

This is not the first vegetable claimed to have been the cause - lettuces, tomatoes and Spanish cucumbers have all been suggested as the source, apparently with poor justification, at one stage or another during the outbreak. Of course, this has stigmatised the growers and in fact has seriously damaged the whole fresh vegetable market in Europe. The American military has ceased purchase of any European vegetables for the military commissaries and may arrange an airlift of fresh vegetables from America, thus contributing to global warming and misery for European vegetable farmers.

I'm not going to comment further on the possible source of the outbreak until I see Pulse Field Gel Electrophoresis data linking bacterial isolates from the sprouts and the patients. This will still not prove that the sprouts are the source, but if the PFGE profile matches, it is strong evidence for a finding.

How do you trace an outbreak? With difficulty!

2011-06-03T17:23:00.000-07:00

The outbreak of E. coli O104:H4 food poisoning in Germany is possibly one of the worst outbreaks on record and certainly one of the most deadly.

Public health officials still don't know the source. Spanish cucumbers were initially blamed, but it appears that might have been wrong, though it does appear that salad vegetables may have been involved.

The investigation of outbreaks like this is a science in itself, but must be frustrating for epidemiologists. Our modern supply chains are extremely complex - foods are sourced from all over the world and suppliers may make up orders from many different primary producers.

André Picard, — Public Health Reporter of Canadian newspaper "The Globe and Mail" wrote a neat article with associated links and videos on the investigative process and its difficulties. I have reproduced part of it below:

"...real life does not have tidy TV endings. Despite determined efforts and great expense, the precise source of poisoning is found in fewer than one-third of outbreaks. But here is a quick look at how public officials try to resolve those puzzles.

First, there is a trigger event – usually people showing up in emergency rooms with violent cases of diarrhea and vomiting that are the hallmarks of food poisoning. Samples – stool, saliva, sometimes blood – are taken. Serious illnesses like E. coli get special attention:
Reporting them to public health authorities is mandatory.

Data from lab tests are routinely sent to local public health authorities and to PulseNet, an electronic database. While most cases of food poisoning are sporadic, patterns can be spotted quickly – there can be a cluster in a single city, or a sudden spike over a wide geographic area. Labs do DNA fingerprinting of pathogens like E. coli that can show if the illnesses have a common source.

In this instance, three deaths of patients with E. coli infection in Germany set off alarm bells. They all had the same DNA fingerprint, strongly suggesting a common food source.
When an outbreak is suspected, epidemiologists (disease detectives) start questioning those who are sick. In these “hypothesis-generating” interviews, patients are asked about specific high-risk foods (such as sprouts or unpasteurized milk) and for detailed recollections of what they have eaten in recent weeks.

This can produce, fairly quickly, a list of suspected culprits. E. coli is a fecal bacterium, for example, so raw foods are a focus. In Germany, a day after the deaths, consumers were warned to not eat tomatoes, cucumbers or lettuce. Three of four cucumbers tested came from Spain, so the country was quickly identified as a culprit in media reports.

Public health officials share information gathered from patients with food safety regulators (such as the Canadian Food Inspection Agency), who try to trace the commercial supplier of a common food source.

In their interviews, epidemiologist collect information on where food is purchased; if many of the patients shopped at the same food chain, for example, the CFIA would identify their vegetable suppliers and try and trace the movement of food through distributors and back to the farm.

But there can be hundreds, even thousands, of suppliers and contamination of food can occur at any point in the process of getting food from the farm to the table – during production, processing, storage, distribution or preparation. Finding the “locus of contamination” becomes an almost insurmountable process of elimination. Currently, farms in Europe that produce vegetables that are consumed raw are being set upon by all manner of investigators who will test products, water sources and so on.

The paradox is that the more people get sick, the easier it is to ultimately find the culprit because the number of food sources they have in common becomes smaller. Often, despite mountains of data, the leads run cold. But the demand for answers does not wane.
The challenge for public health officials and regulators is finding the right balance. They issue speculative warnings like “Don’t eat Spanish cucumbers,” but more often than not they are wrong, and that can cause grievous damage to food producers.

At the same time, acting slowly and waiting for a definitive answer on the source can result in countless cases of illness and death, and still no definitive answer.

To read the full article and access the video clips, click here.

Not all reporting is of this quality; even the BBC has broadcast a news item labeling E. coli as "a virus". Didn't the reporter talk to an expert, or even a Level 6 food science student?

Evolution in action

2011-06-02T15:41:00.000-07:00

Over the last three weeks, a rare form of Escherichia coli has made an appearance in Germany.

E. coli is a normal inhabitant of the gut of man and animals and is found there in very large numbers. They are mostly harmless and actually help us by producing vitamin K. However, some strains are pathogenic and cause diarrhoea.

Individual strains are recognised by their antigenic signature. The antigens are found on the surface of the cells, on the flagella and in the capsule that surrounds the cells. Thus one of the strains that hits the news quite frequently is referred to as O157:H7.

The strain now causing havoc in Europe is E. coli O104:H4. This has rarely been seen as a cause of disease. However, the current outbreak is shaping up to be one of the most dangerous ever seen.

Why has this happened?

That's a question that none of us can answer yet, but the information on this strain is growing rapidly. It can produce a very damaging toxin, called Shigatoxin. The bacterium causes bloody diarrhoea, which is bad enough in itself. But bacteria producing this toxin can also go on to produce Haemolytic Uraemic Syndrome, normally affecting around 2 to 10% of patients, who are often very young or immunocompromised. However, O104:H4 appears to be very virulent and around 30% of patients, who were not in the high risk group, have developed this life-threatening syndrome. So far, 18 people have died.

The fact is, bacteria evolve very rapidly. We see one strain develop resistance to an antibiotic and soon other strains become resistant too. This happens because bacteria can exchange genetic information by a number of different mechanisms. The rate of mutation might be very small, perhaps one in 10 million replications produces a mutant and most of these mutations are probably lethal. However, a single cell can potentially produce a population of around 17 million cells in 8 hours. That allows for a lot of mutations. If even one of these mutants has some advantage over the rest of the population, or at least no disadvantage, the mutation will spread through the population.

This might surprise you, but bacteria also suffer from virus infections. These viruses, or bacteriophages, invade the cells and cause them to make more virus particles before bursting open to restart the infection cycle. Occasionally, the new virus particles contain a bit of bacterial DNA and transfer it to the next host. Sometimes, whole genes can be transferred.

It appears that O104:H4 has not only the Shigatoxin gene, almost certainly transferred by bacteriophage, but has also picked up some other virulence factors. This is why it is so dangerous - the toxin is very damaging to human cells, particularly in the kidney, and the bacterium appears very capable of initiating infection.

I believe we are seeing evolution in action. A normally benign bacterium has become a killer.

Sarah Carter - confusion reigns

2011-05-26T22:47:00.000-07:00

On 12th March, 2011, I wrote about the tragic death in Chiang Mai of Sarah Carter.

Originally, her death was blamed on consumption of toxic seaweed. At the time, I suggested that this was a highly suspect conclusion, based on the symptoms and the circumstances.

A short while later, it was claimed that Sarah and her two friends had been infected by an ECHO virus. The symptoms matched.

However, more information came to light - a Thai tourist guide had died in the next room in the same hotel and a week earlier, two other tourists had died in a room one floor below.

The New Zealand TV3 channel discovered that a total of seven tourists had died in Chiang Mai in similar circumstances. Sara Hill, an investigative reporter for TV3, went to Chiang Mai and made a programme screened here a couple of weeks ago.

In an interview with Sarah Carter's friend, Sara Hill discovered that none of the three girls had eaten seaweed and had eaten two different meals. They all developed sore stomachs and vomiting and were hospitalised. According to a Thai cardiologist, Sara Carter suffered very low blood pressure, dehydration and low blood flow to the kidneys, with ultimate kidney failure.

The reporter managed to obtain swab samples from the room occupied by Sarah and returned them to New Zealand for testing. Traces of chlorpyrifos, an organo-phosphorus insecticide used in corn and cotton farming, were found in the swabs. Dow Chemical Company voluntarily withdrew the registration of chlorpyriphos for domestic use in 2001. Mr. Ron McDowell, a UN scientist, hypothesised that Sarah had been exposed to chlorpyrifos as a result of over-zealous spraying of the hotel room to control bed bugs by a pest control operator. McDowell claimed that the symptoms and pathology all fitted with chlorpyrifos poisoning.

However, the swabs were taken three months after the room was occupied by Sarah, so spraying could have occurred at any time during those three months. The report form was shown in the programme. The level in Sarah's room was given as <0.1 microgram/sample, which probably means "below the limit of detection". A sample from an air conditioner was 0.24 micrograms/sample, but the film of the sample being taken suggested that the area swabbed was uncontrolled.

The half life of chlorpyrifos in the human body is about one day, so, although it is absorbed quickly, it also disappears from the body quickly. Thus tests at the hospital may not have shown its presence in Sarah's body.

I'm not convinced that we are much further forward. The Thai authorities were not being particularly cooperative with the TV3 investigation and recently refuted the chlorpyrifos theory. Three toxicologists in New Zealand have issued a statement criticising the programme and the conclusions drawn by the experts consulted by Sarah Hill.

It looks as though seaweed is off the hook and food poisoning seems a bit unlikely, as the three girls ate different meals, but suffered similar symptoms not commonly seen in microbial food poisoning. Food contamination is not completely ruled out, as several meals could have been contaminated with a chemical.

I don't know if we will ever know the true story

Kiwifruit dumped

2011-05-13T16:23:00.000-07:00

It's been a mixed year for New Zealand kiwifruit growers. Earlier in the season, some vines were found to have been infected by Pseudomonas syringae pv actinidiae (Psa) - a bacterial disease first identified in Japan about 25 years ago. The Asian strain causes leaf spotting and some die-back of vines, though it is far less savage than the Italian strain that has also been found in one area.

In the last week, 100,000 trays of kiwifruit have been withdrawn from the market (some had already been shipped and will be intercepted) and will be destroyed. It appears that a worker on a harvesting gang has been diagnosed with typhoid, picked up overseas before arrival in New Zealand. Since it is not possible to isolate the specific fruit handled by the worker, all the fruit picked by that gang has been withdrawn.

The risk of infection being carried on the fruit is very low, but Zespri, the main marketer of New Zealand's $1.5 billion kiwifruit export industry, has been cautious and manned up, taking the pro-active response to prevent any possible disease risk for consumers. This action is in stark contrast to those of some overseas companies that have attempted to conceal the potential of their products to cause harm to consumers.

The value of the withdrawn fruit is around $800,000 and represents less than 0.1% of this year's expected kiwifruit exports. However, the unfortunate growers may not be insured, so this will be a serious loss to some orchardists.

Tyhpoid is caused by Salmonella enterica enterica, serovar Typhi, a bacterium that infects the intestine, resulting in damage to the intestine and fever. Resultant diarrhoea can lead to transmission of the bacteria to other people and the environment.

The disease was named from the spike in infections observed after severe typhoons. The contaminated water and poor sanitary conditions that followed the typhoons provided the conditions for increased numbers of infections.

Mary Mallon was an itinerant cook, having arrived in America around 1874 from Ireland. She became a domestic servant and eventually a cook in New York. Though she appeared healthy, between 1900 and 1907, Mary had seven cooking jobs where 22 people became ill and one died of typhoid. After an investigation, Mary was taken by force and held against her will without trial. This occurred at a time when the symptomless carrier state was unknown, so the investigation was quite innovative. Mary was effectively imprisoned under sections 1169 and 1170 of the Greater New York Charter and lived alone in a cottage on North Brother island.

After her release, Mary eventually went back to cooking and this time was sent to the island for a period of 23 years, which ended only when she had a stroke. She died six years later.

Mary was then and is still known as Typhoid Mary.

If you want to read more about Mary Mallon, go to Jennifer Rosenberg's 20th Century History page:

Hazard or Risk?

2011-05-08T22:34:00.000-07:00

The words "Hazard" and "Risk" are often used rather loosely in everyday speech. e.g. "Cycling to work in Auckland is a risk". What does this mean?

I read an article today that attempted to clarify the situation. Unfortunately, the writer got it wrong and increased the possible confusion.

In terms of food safety, a hazard is something that has the potential to harm the health of the consumer, such as the presence of a piece of glass in a cheesecake. Hazards may be biological, chemical or physical.

The risk is the probability of the hazard occurring.

The other thing we need to consider is the severity of the outcome.

Let's take a non-food example to show the importance of understanding these terms.

The hazard under consideration is getting hit by a wheel falling from an airliner.

We know that the risk (probability) of this happening is very low.

But if the event does occur, the severity of getting hit by falling debris is very high, possibly lethal.

Now think about hazard, risk and severity in the food safety context.

Walls have ears and bacteria have antibiotic resistance

2011-04-30T19:06:00.000-07:00

Recently, I was having my lunch at a conference and couldn't help overhearing a conversation between two people sitting alonside me. I suppose I should have tried not to listen, but their discussion was in my own field.

It appeared that one of them had read a survey conducted on the bacteria isolated from poultry in USA. Even "organically grown" chicken contained bacteria that displayed multiple-antibiotic resistance. This implies that the chicken farms may be using antibiotics in the flock rearing operation, though it doesn't necessarily prove the point.

Without getting into the rights and wrongs of using antibiotics in rearing of "organically grown" poultry, this does point to a wider concern: that farmers may be using sub-therapeutic levels of antibiotics widely to improve growth rates and yields of all meat animals. Any bacteria that survive and grow in the presence of antibiotic are likely to be resistant to the chemicals and if these bacteria should go on to infect humans, those antibiotics will be useless for treatment.

I'm not sure if these people were talking about a survey*** conducted by the Translational Genomics Research Institute (TGen) in Arizona. These scientists tested 136 samples of 80 brands of beef, chicken, pork and turkey collected from 26 retail stores in five US cities. They found that nearly half of the samples contained Staphylococcus aureus and that just over half of these isolates were resistant to at least three classes of antibiotics. Further analysis suggested that the bacteria were from the animals and not from the processing factories, again indicating that antibiotics had probably been used in rearing the animals.

It might make meat more expensive, but I believe that governments must force the reduction in the amount of antibiotics used in animal rearing if we are to avoid catastrophic consequences for the human population in the near future. Remember: it has been estimated that the cost of getting a new drug onto the market is now between 2 and 3 billion dollars. We aren't going to get many new drugs at that rate.

*** The full report is available at:

http://dx.doi.org/10.1093/cid/cir181

(The report is a technical report, intended to be read by other scientists, but anyone should be able to follow the discussion).

Tasty but occasionally dangerous

2011-04-15T20:02:00.000-07:00

If I asked you to name a food group that might be implicated in food poisoning, you would probably respond with "meat". I did a survey (n=1) at home today and got that answer. My wife thought a bit longer and said "Custard, but that's only because you have influenced me over the years".

Baked goods probably don't spring to mind as potential carriers of food poisoning bacteria.

In the last week, there have been reports from Rhode Island of zeppole, or St. Joseph's Day cakes, causing food poisoning by Salmonella. I had never heard of zeppole before this report, but they are apparently popular in Italy, Sicily and Malta and in the Italian-American communities in the United States and date from the early 19th century. They are deep-fried dough balls, or sometimes choux pastry, topped with powdered sugar or filled with custard, pastry cream or a mixture of butter and honey. They sound delicious, though perhaps dangerous for the figure!

At the time of writing, there have been 76 cases and 29 hospitalisations. Two people have died from Salmonella-associated illness. It is too soon to say how this happened, but the possibilities include a carrier of Salmonella working as a food handler, or the use of ingredients contaminated with Salmonella. The deep-fried pastry would probably be sterile immediately after frying, but could be contaminated by the food handler during the filling process.

Breads, fruit cakes and biscuits are usually pretty safe by virtue of low water activity, but filled pastries receive quite a lot of handling, while real cream may be contaminated with bacteria that rapidly grow under abuse temperatures to the point where they can cause food poisoning, either by infection or intoxication.

Will spoiled food make you sick?

2011-04-04T22:58:00.000-07:00

I recently received a message from Jo, asking me to comment on this subject. Jo actually raised a lot of questions and, of course, the answers are not simple.

First question: If the food smells off, tastes bad, has a poor colour etc. is that a good indicator it will make you sick?

Humans have been on the Earth for a long time and one of the reasons they have survived for so long is that they have evolved self preservation mechanisms. If the food smells off or doesn't look right, there is a chance that it is poisonous in some way and we tend to avoid it. Sometimes I wonder what the first people to taste durian or blue cheese thought they were doing! So, clearly, the answer has to be a qualified "Yes, it might make you sick, but some sort of tribal wisdom suggests that a few foods can look and smell awful but still be OK to eat".

Jo then went on to say that she thought that the food was unlikely to make you sick, as the changes were caused by spoilage bacteria and enzymatic reactions, which are not the same as pathogenic bacteria, which she thought do not alter the food in the same way.

This is where it gets complicated. Spoilage bacteria do cause some changes, which, by definition, make the food unacceptable to most people. Other bacteria, such as Salmonella, may grow alongside the spoilage bacteria. When the food is eaten, the salmonellae set up an infection in the gut and produce the familiar food poisoning symptoms.

Second question: Is it true that pathogenic bacteria don't alter the food? Again, it depends on the bacteria. Generally, clostridia alter the food a lot, producing many smelly compounds and gas. This would put most people off eating the food, so they would be safe. But some Clostridium botulinum strains are non-proteolytic. That is, they don't break down proteins and they don't produce the foul smells that the proteolytic strains make. So you could find improperly processed canned foods that appear quite normal, but could kill you.

Jo's third question was perhaps the most fascinating: she was most interested in how the food could potentially have both types of bacteria on it near to the time it was made and correctly identified contamination of the food as the cause, possibly by cross-contamination from some source. A good example would be a careless food handler.

At this point, the food could cause food poisoning if consumed - Salmonella transferred from raw meat to a cream pastry would be a good example here.

Jo went on "However as time goes on and assuming the food gives them all the things they both need to grow, is it as simple as the pathogens might be around for a short time until the spoilage guys, who being better competitors for resources, take over; so by the time the food
is showing signs of being spoiled, the pathogens have been killed off?"

That's a really insightful comment. Many fermented foods are actually safe because of this pattern. Take raw cabbage and make sauerkraut: we shred the cabbage and add about 2.5% salt to it and then press it into a container and seal it. The salt draws out the tissue fluids from the shredded leaves and bacteria naturally on the leaves begin to produce lactic acid. If we sample on the first day, we can find all sorts of bacteria, including Escherichia coli and possibly Salmonella. However, as more acid is produced, the pH falls and the potential pathogens die off. Finished sauerkraut has a pH around 3.1 to 3.7 and is perfectly safe to eat, though there has been a lot of bacterial growth in it.

So, to return to Jo's original question, "Is spoiled food potentially safe to eat, even though it looks and tastes awful?" Sorry Jo, I can't answer that. But if it tastes awful, why would you want to eat it?

One last point: there is an anecdote that a lady opened a can of peas and thought that they looked a bit different. She tasted one and cooked the rest. She died of botulism. Ironically, if she had cooked them and then tasted one, she would have lived, as the botulin toxin is heat labile. I don't remember where I read this - it was somewhere around 1980, but it's a good example with which to finish this article.

Poor Understanding - Raw Milk in New Zealand

2011-03-27T02:37:00.000-07:00

Last week, I read an interesting article by Jill Galloway in the Manawatu Standard entitled "Selling milk as it was meant to be". The story was about the increasing sales of unpasteurised and non-homogenised milk at the farm gate. Unfortunately, the author and/or her interviewees made a number of errors.

Under New Zealand law, sales of raw milk from the farm gate have been permitted for several decades. All other milk and milk products must be pasteurised or given an approved alternative treatment. Section 11A of the Food Act 1981 allows for producers to sell up to five litres of raw milk at any one time from their farm gates to people who intend to consume it themselves, or to provide it to their families. However, the milk must be harvested under an approved Risk Management Programme under the Animal Products Act 1999.

So if farmers follow the rules, there should be no problem about safety.

However the article went on to express some strange views.

For example: "People believe in the integrity of food. People want to know where it comes from. Processing destroys dairy products".

Or how about: (Farmers) "are up against rules, regulations and science".

But my favourite was: "Before processed milk, there was no heart disease. Homogenisation means the fat particles are small enough to be ingested, not digested, and go straight through to the blood and arteries," Ms M. says. She thinks homogenisation began because people thought the fat on the top of milk was bad and they did not want to see it.

Hang on a minute. If Ms M. is correct, then the dairy companies are actually delivering what consumers are demanding.

Second place goes to Farmer C: "When it is pasteurised, the milk becomes dead. People don't want to be eating or drinking dead stuff."

So you never had a steak, Mr. C?

I guess I should not poke fun at these people, who genuinely believe that their product is better than pasteurised milk. And indeed, they are producing their product according to the NZFSA regulations. But it does worry me that people can be so smart in some aspects of their lives but authoritatively make such ignorant statements.

A bridge too far for Bio-enterprise?

2011-03-23T13:33:00.000-07:00

If you look back over the posts of the last three years, you will see that the vast majority are about microbiological food safety issues. There are other safety concerns, not all of them justified.

If you were going to fly from Seattle to Los Angeles, would you go via Hong Kong? Not unless you were forced.

I have just returned from the NZBio 2011 conference, where the theme was "Enabling Successful Bio-enterprise". The conference was attended by delegates from far and near - businessmen, entrepreneurs, venture capitalists, regulators and scientists. Over three days, I heard papers on drug development, bio-fuels, bio-marker molecules and bio-plastics. I didn't hear a single paper on food.

This surprised me. When I began my career, I helped to develop the ICI Single Cell Protein process. This was a high-tech attempt to solve a perceived looming food shortage. The development was a technical success, but an economic failure. The cost of feedstock rose dramatically and, even back then, the costs of testing and getting approval for human or even animal feeding were prohibitive. The protein was high quality, but there were difficulties of acceptance and the public probably thought that it was too reminiscent of sci-fi foods. The SCP concept was, perhaps, an approach to food supply ahead of its time.

Now, through beautifully sophisticated molecular biology techniques, we have the opportunity to produce more food, with desirable characteristics such as longer shelf life, slower or faster maturation, better nutrition and better functionality.

Why are bio-enterprises not taking advantage of these procedures to increase our food supply and are instead choosing to manufacture medical test kits, bio-fuels and making the very risky investment in new drugs?

I think the answer lies partly in the massive misinformation campaign against genetic manipulation and safety of Genetically Modified Organisms (GMO). There; I named the elephant in the room. The public has been so mislead about genetic manipulation that bio-enterprises consider that it is just too financially risky to invest in GM products.

I questioned a panel of experts about this. The consensus of those prepared to comment was that foods derived from GMOs will be accepted and on the market in 10 to 20 years. Currently, research and development organisations are going to great lengths to get to a product they could achieve much more quickly and easily by genetic manipulation. This is like forcing a mechanic to fix your car with stone tools or doing the SEA - HKG - LAX trip.

Currently, there is no real shortage of food, just a maldistribution. But the growing world population and increasing lifestyle expectations will eventually lead to food shortages. GMO-derived foods may help to alleviate these shortages and add to the arsenal of functional foods and nutraceuticals. This will not happen until the safety of GMO-derived foods is demonstrated, the public begins to trust scientists again and the misinformation campaigns are shown for what they really are.

I don't claim to be an expert on GMOs. If you want to follow up on the safety of GMO-derived foods, have a look at:

Assessment of the food safety issues related to genetically modified foods. Harry A. Kuiper, Gijs A. Kleter, Hub P. J. M. Noteborn and Esther J. Kok (2001) The Plant Journal 27(6), 503-528

Black Humour

2011-03-16T00:25:00.000-07:00

I have been a consultant to the food industry for the last 33 years and in that time, I've seen some things that would be funny if they were not so disturbing.

A few years ago, I was helping a food factory to gain control over the level of contamination in their products. The company manufactured a very large number of product lines, some of which were essentially assemblies of cooked foods with fresh salad vegetables. The levels of microbial contamination in finished goods were obviously not under control and sometimes spiked well above the Microbiological Reference Criteria for Foods.

The company was doing regular wash down of the entire production facility, though their finished goods still showed irregular spikes of contamination. I began doing regular checks of hygiene in the factory. I asked them to change the way that the cleaning was conducted, so that there was no food exposed during the cleaning and that the equipment was cleaned top-down. The product contamination continued.

On several occasions, I pointed out that they were cleaning the food contact surfaces well, but that the fabric of the factory was not being cleaned so well, particularly the floors. Some of the mutterings went along the lines of "We don't process food on the floor". Yes, of course, but wet floors allow growth of bacteria in food residues and generation of aerosols, which can settle onto food contact surfaces and in-process food.

The last straw came when I pulled up a floor drain and showed the manager the thick gray biofilm on the fitting. This can't form overnight or during a shift - it had not been cleaned for at least a week. The manager responded with "That's not our biofilm". Being an erudite conversationalist, I said "Huh?". "No", he replied, "the drains back up and that's how the biofilm gets there, but it's not ours".

Hands up all those who are surprised that this manager successfully managed the company into receivership. Nobody? Thought so.

Toxic seaweed was a red herring

2011-03-12T15:47:00.000-08:00

The tragic death of beautiful Kiwi backpacker, Sarah Carter, in Thailand last month was initially blamed on a meal containing toxic seaweed. Sarah and two other women suffered vomiting and heart complications while they were staying in Chiang Mai. Privately, I thought that this explanation was highly unlikely, partly because of the symptoms and partly because it appeared that only these three were poisoned.

It now seems that Sarah had been infected with an ECHO virus. These Enteric Cytopathic Human Orphan viruses are found in the gastrointestinal tract and primarily cause disease in children. (Their name originated in the 1950s, when cell culturing allowed the viruses to be identified, but no disease was associated with them).

ECHO viruses are highly contagious and exposure to them can result in an infection of the lower intestine, which then spreads to other organs. Death is usually the result of overwhelming liver failure or myocarditis (inflamation of the heart muscle).

Because of their association with the gastrointestinal tract, ECHO viruses are usually transmitted by unhygienic conditions and person-to-person transmission via the faecal-oral route. Respiration of infected droplets and contact with fomites (contaminated objects) may also be important in transmission. I believe that it is significant that three other people died of heart problems in the same hotel in the space of two weeks, though a doctor from the Thailand Department of Disease Control said that the elderly British couple who died both had blocked arteries.

I guess that the messages we can take from this tragedy is that foreign travel is wonderfully mind-broadening, but that visiting areas where environmental and food hygiene are poor can be hazardous to health. We should be careful, however, before thinking that Asia is the only
place we can contract ECHO viruses - poor hygiene can be found in any country.

You can lead a horse to water, but you can't make her drink

2011-03-06T16:09:00.000-08:00

Another saying from my childhood, translated from the original Yorkshire dialect into English!

What triggered this? Well, HACCP (Hazard Analysis and Critical Control Points) has been around since 1959, when NASA attempted to ensure that food fed to astronauts would not make them ill, or cause injury. The possibility of early astronauts, trapped in orbit and vomiting into their helmets, could not be contemplated. Originally developed as a microbiological safety programme by the US Natick laboratory and later by The Pillsbury Company, the Modes of Failure programme eventually covered all aspects of astronaut food, not just microbiological hazards. By 1971, the HACCP system was published and documented in the USA and by 1985, the National Academy of Science recommended the use of the system. Incidentally, I began teaching HACCP to food technology undergraduates in New Zealand in 1978.

Recently, Roy Costa posted an article on Food Safety and Environmental Health Blog:

http://www.safefoodsblog.com/2011/03/articles/outbreaks-1/schools-skip-out-on-haccp/

in which he pointed out that retailers demand food safety management systems from suppliers. The end of the supply chain - institutions and food service organisations - are also required to have HACCP-based food safety plans in place, but schools seem to have dropped beneath the regulatory radar: few have implemented the requirements and they are not being pursued by the local health departments. Costa suggests that this is because the schools and health departments are both part of the counties, which claim that this is an unfunded Federal Government mandate.

Politics aside, this problem of lack of implementation of HACCP-based food safety plans is not restricted to schools and food service outlets.

Some years ago, I wrote an HACCP-based food safety programme for a local food manufacturer. This is not something I will do again; as a consultant, I was an outsider and though I had a close familiarity with the factory, I don't think that the production manager wanted to do more than "tick the box" that they had a programme.

About a year after I wrote the programme, one of my students got a job at the factory. "What do you think of the HACCP programme?" I asked. "What programme?" he replied, "I never saw it". The next time I visited the factory, I mentioned this to the manager. He said "Oh, I'm sure it's around somewhere, probably on the shelf in my office".

So, after that roundabout story, we come back to the title of this posting. The factory complied with the regulations - it had an HACCP-based food safety programme, so any auditor could be shown the document. But just having a nicely bound document on the shelf is only the beginning. The plan must actually be implemented in the factory and reviewed on a regular basis. This manager wasn't even sure where it was, his staff didn't know of its existence and there is no doubt in my mind that he never reviewed it.

More on Listeria contamination of vegetables

2011-03-03T13:05:00.000-08:00

On 18th January 2011, I wrote about the withdrawal of salad vegetables from certain supermarkets in New Zealand because of possible contamination by Listeria (See Listeria Hysteria).

This week, I came across a paper published in Food Microbiology, describing the transfer of Listeria innocua from contaminated compost and irrigation water to lettuce leaves. (M. Oliveira et al. Food Microbiology 28 (2011) 590-596).

These authors noted in their introduction that "Fresh produce can become contaminated at any point during the primary production, processing, distribution and preparation. Primary sources of preharvest contamination include soil amended with untreated or improperly composted manure, contaminated irrigation water, the presence of wild and domestic animals, infected workers, and unclean containers and tools used in harvesting. Research has demonstrated that many human pathogens are able to survive for extended periods in soils, manure and water."

Listeria monocytogenes causes Listeriosis, a rare but serious disease in humans, with an incidence of 2-3 cases per million of the total population in England and Wales.

In their experiments, Oliveira et al used an avirulent strain - Listeria innocua. They transplanted lettuce seedlings into pots containing soil and contaminated compost; compost manually surface irrigated with contaminated water after the seedlings were transplanted; and treated a third set of seedlings by hand-spraying contaminated irrigation water onto the lettuce leaves after transplanting.

These workers reported that the lettuce leaves became contaminated with Listeria from the soil and, not surprisingly, sprinkling with contaminated water also resulted in contamination of the leaves with Listeria, which survived for some days. The bacteria survived in the compost for more than 9 weeks, giving ample opportunity for contamination of the leaves by transfer of soil.

Clearly, as these workers showed, irrigation water used for fresh salad vegetable growth must be pathogen free and manure used in compost must also be treated to remove pathogens.

To flush or not to flush?

2011-02-07T02:19:00.000-08:00

No, this one isn't about faecal bacteria, at least not directly.

Our major TV news broadcaster was guilty over the weekend of a dreadful beat-up on the use of gas mixtures to extend the shelf life of fresh meat. Under the banner of "How safe is your meat?", the channel made a big deal of the use of gas mixtures containing carbon dioxide to inhibit bacteria on the meat. They implied that suppliers were trying to pass off old meat as "fresh" and that the process was used to make the meat look redder and thus deceive the consumer into thinking that the meat was fresher. A further implication of the banner was that gas flushed meat is unsafe. Must have been a slow news day.

Meat technologists and microbiologists have known for many years that gas mixtures containing carbon dioxide inhibit bacteria, such as Pseudomonas, which are responsible for the development of slime and odours on meat stored under refrigerated conditions. The gas also inhibits many pathogens, which may potentially cause disease.

Consumers interviewed in supermarkets said that the meat should be labeled to indicate that it had been gas flushed. Of course, one supermarket chain said they would do this if customers wanted it, while another tried to take the high ground and claim that they would never gas flush meat.

This is all playing on the ignorance of many consumers about food technology and food safety. Certainly the meat keeps longer when gas flushed. Why does meat normally have such a short shelf life? Because some bacteria can grow under refrigeration conditions and turn the meat slimy or produce odours that consumers find objectionable.

Should we ignore and reject the many years of research on food preservation? Should we perhaps go back to taking meat home wrapped in paper and cooking it the same day? That's "natural". Should we reject vacuum packaging - it's not natural, but in fact works in a very similar way to gas flushing. Consumers have demanded longer shelf life in all sorts of foods - meat, strawberries, smoked mussels, cakes and pastries. In response, food technologists have developed ways to deliver such foods and these techniques involve preservative chemicals, vacuum packaging, pasteurisation and gas flushing (modified atmospheres). If we are prepared to go back to foods with a shelf life of just a few days, we can reject gas flushing and other technologies.

If consumers are really concerned about gas flushing, they can recognise flushed packs by the fact that the film is sealed to the tray, or in some cases, such as gas flushed bakery goods, the package looks like a pillow.

Me? Well, I'll happily buy carbon dioxide flushed meat - it keeps longer and in some cases looks better.

Poor quality of reporting

2011-01-19T18:16:00.000-08:00

I have just read a couple of articles in a national newspaper. These report on the recall of bagged salads because of possible Listeria contamination and the death from avian botulism of wild birds in Auckland.

Listeria monocytogenes is a bacterium that causes a rare, but serious disease in humans. (See Listeria hysteria). The first article includes an information box, in which the symptoms are described as "a mild viral infection". Bacteria are not viruses and the two entities are as different as lobsters and soft cheese!

The second article describes the increase in numbers of wild birds dying because the very warm water temperatures (up to 26C) have allowed rapid proliferation of Clostridium botulinum, which produces a neuroparalytic toxin. The information box in this article claims that "the toxin thrives in still, shallow, warm water". The toxin does not "grow or increase in bulk", though the bacterial cells that produce it may do.

Neither of these errors is likely to result in injury if the reader follows the advice in the articles, but it is just plain, sloppy reporting. Google lists 1.16 million articles on L. monocytogenes and 541,000 on C. botulinum, so there is no excuse for the reporters' not having done a bit of background reading. We all make mistakes in our writing, but if we set out to educate, then we really ought to check the simple details.

I stand ready to get hammered if this blog contains stupid errors!

Avian botulism is caused by Type C toxin, which does not affect humans.

Listeria hysteria

2011-01-18T20:20:00.000-08:00

Foodstuffs Own Brands in New Zealand has this weekend recalled baby spinach and various salad mixes because of possible contamination with Listeria.

The recall was reported in newspapers and picked up by TVNZ news and given a special segment in the evening Close Up current affairs programme. Unfortunately, it was given the same sort of treatment as might befit a tsunami.

In my opinion, Foodstuffs has done the right thing - they know that there is a problem with a product from their supplier and they have withdrawn it from the market to protect their consumers' health and their reputation.

But the presence of Listeria in salad vegetables is practically impossible to avoid. The Microbiological Reference Criteria for Foods note that all foods produced by a process which is capable of achieving a Listeria-free product should test negative for L. monocytogenes in 5 samples of 25g. (Reference Criteria are guidelines to indicate when food can be considered unacceptable or unsafe). The criteria do not apply to raw fruits and vegetables, and bagged salad vegetables do not receive a listericidal process.

Where does L. monocytogenes come from? The bacterium is widely distributed in the environment and can be found in decaying vegetation, soils, animal faeces, sewage, silage and water. It is not surprising that salad vegetables will sometimes be contaminated from these sources.

Most bagged salad vegetables are given multiple washes, culminating in a chlorine rinse, which can reduce the levels of L. monocytogenes by a factor of about 10 (a 1 log reduction). Provided that the numbers of L. monocytogenes are less than about 100/g at the point of consumption, they are unlikely to cause disease. Many producers recommend re-washing at home before consumption. However, it's difficult to dry the leaves and dressing doesn't stick to wet leaves, so it is likely that this recommendation is often ignored. Refrigeration is also recommended, but it is probably better to take note of the 3-4 day shelf life, as Listeria can grow in the refrigerator, albeit slowly. Growth is much less likely on dry, uncut surfaces.

The levels of L. monocytogenes required to cause disease are very difficult to assess and this is reflected in the varying compliance criteria adopted by different countries. Listeriosis is a rare but serious disease in humans, despite frequent exposure to the causative organism, with an incidence of 2-3 cases per million of the total population in England and Wales. Those most at risk are, in descending order, organ transplant patients, patients with AIDS or HIV, pregnant women and their unborn babies, cancer patients and the elderly. New-born infants may also be infected from their mothers or other infants. Non-pregnant healthy individuals are highly resistant to listeriosis.

What does this all mean? Basically, if you look for Listeria in vegetables in the marketplace (and vegetables grown in your own garden) you will sometimes find it. Various surveys suggest that the frequency of detection will be between 1 and 86%. If a sample does test positive for Listeria, efforts should be made to find and eliminate the source of contamination. The frequency of sampling should be increased and subsequent samples should test negative.

There is no room for complacency, even in companies that have never had a positive Listeria test, but a single positive sample should be viewed with a modicum of restraint.

Why do people buy insurance?

2010-12-17T17:58:00.000-08:00

Do you sometimes think "Why do I keep paying insurance premiums for my car, boat, house, personal liability, camera etc? I hardly ever make a claim". In all the years I have been paying premiums, I have only once made a claim on my car insurance, and that was when one of the local semi-evolved simians stole it and drove it into a ditch. Would you consider not insuring your house? Would you be able to continue with business as usual if your offices burned down? The chances of making a claim and getting some of the premiums back are quite small.

The probable reason we continue to pay is that it gives us peace of mind, knowing that if we do smash the car into a BMW or Rolls Royce, we won't be bankrupted by the repair bills for the other car. We can drive, secure in the knowledge that we have that one covered.

Pasteurisation of milk is insurance and free. A mild heat treatment kills all the pathogens that might have got into the milk during milking and transport, leaving the nutritional value essentially unchanged. Why would you even consider drinking raw milk or eating raw cheese, knowing that there is a small chance that it could result in illness that would change your life or that of your family for ever? There has been plenty written about the dangers of Escherichia coli O157:H7 and other STECs, so I'm not going to go over it again here. (See other posts on E. coli by clicking the E. coli label at the RHS of this blog).

Please, this Christmas season, if you really want to eat and drink raw milk products, you can make an informed choice. But don't give these products to children - they don't have that choice and a dose of E. coli O157:H7 can lead to HUS, which will probably ruin the rest of their lives.

Microbial tongue twisters

2010-12-16T17:46:00.000-08:00

Today Bill Marler published a link to a clip of Larry King making an ass of himself while introducing a segment on Escherichia coli.

http://www.youtube.com/watch?v=omaF9kA94Io&NR=1

Perhaps it's a good thing he used the abbreviation E. coli

That set me thinking. Does the general public find the names of bacteria so difficult to pronounce that they put all thoughts of them to the back of their minds? Or do they regard all bacteria as "germs"?

The difficulty is that there are literally thousands of different bacteria, so microbiologists have to give them names that mean something and so that they can be grouped for study. Sometimes the genus is named after its discoverer, or in honour of a famous microbiologist. Salmonella was named after D.E. Salmon, an American bacteriologist; Bacillus is named from the Latin noun meaning "a small rod", while Acetobacter is so named because it oxydises ethanol to acetic acid (vinegar).

When microbiology students start out, they often have difficulty in remembering, or even pronouncing, names like Vibrio parahaemolyticus and Pediococcus pentosaceus. Small wonder that the rest of the population has problems.

In fact, in terms of food poisoning, Joe Sixpack doesn't need to know these names. Basically, if you mistreat food by contaminating it, or by holding it at temperatures that permit growth, there is a possibility that numbers of pathogenic bacteria will increase to what is termed an "infecting dose" or that toxins will be secreted into the food. The latter cause food poisoning when ingested. So what is our favourite bloke going to do to keep himself and his family safe?

Easy - clean, cook, cover and chill. This little mnemonic includes it all: Clean-handle all foods with clean hands and utensils; Cook frozen foods after proper defrosting and use a thermometer to ensure that poultry or meat patties are properly heated through. If foods are to be reheated, ensure that the temperature reaches at least 75C right through to the centre; Cover cooked foods during cooling and place in the refrigerator within 30 minutes; Chill foods to 4C and hold at that temperature until served (remember that some bacteria grow readily at refrigerator temperatures, so even chilled food will not remain safe forever) or hold above 60C. You can find more extensive guidelines for these important concepts on the MAF website in New Zealand, or the FDA sites in America.

In the Southern Hemisphere, we are at the start of the barbecuing season. It's important to be really careful - never put cooked meat on the same plate as raw meat and pre-cook chicken legs etc. making sure that patties are heated right through.

I was once at a company barbecue, standing in line to collect my meal. I heard someone behind me whisper "See what he takes, he's a microbiologist". I didn't need to name the bacteria that might have survived on my meats, choosing only steak and thoroughly cooked burger patties.

Make those bacteria do the 100m hurdles

2010-12-11T23:37:00.000-08:00

When I was a kid (last century) at Grammar School in the UK, taking part in athletic activities was compulsory. One event that sticks in my mind is the 100m hurdles. It's important to get a rhythm going and take the same number of steps between the landing and takeoff for each hurdle. This seemed to go well for the first two or three hurdles, but it often became apparent that I was progressively falling short of my takeoff point for the later hurdles. Eventually, I either stumbled or had to take a couple of extra steps.

This principle is applied to modern food preservation. "Hurdle Technology" is a term coined by Lothar Leistner in about 1985. The concept is simple. Set up a series of "fences" and force bacteria to jump over them; if they don't fall at the first one, a later fence may trip them. In food, the fences are low levels of preservatives, modified atmospheres, special packaging, low temperatures, acid pH and so on. Some bacteria will be able to grow at refrigerator temperatures, but not in acid, or without oxygen etc.

There is a tendency among consumers to regard food processing as something sinister thought up by food technologists and done by manufacturers; fresh food is somehow better. In fact, by use of multiple hurdles, food can be kept for longer and the amounts of preservatives in the food are reduced without compromising safety.

Do you really understand what's unsafe about your food?

2010-11-15T17:50:00.000-08:00

There is a lot of concern about the safety of food. There is also a lot of misinformation and misunderstanding. Most of us have some concept of the dangers of the modern world, but our perception of risk, i.e. the probability that the hazard will become manifest, is often wide of the mark, perhaps influenced by publicity.

For example, most of us know that smoking is hazardous and that the risk of lung cancer and heart disease associated with smoking is high. Ask someone about the risk of flying in an airliner. If there has been a crash in the recent past, they may respond that flying is a high risk activity. The truth is that flying on a scheduled commercial flight is very safe. It's just that if an airliner crashes, it makes the news headlines all around the world, which influences our thinking.

Quite a long time ago, so long that I can't find the original reference, a few simple questions were put to food consumers. Food scientists assessed the actual risks. These people were asked "What is the food safety risk posed by the following?" What would your responses be?

Risk factor                            Perceived risk                    Actual risk

Microbial contamination              Low                                  High

Packaging failure                         Low                                 High

Pesticide residues                       Medium                            Low

Irradiation                                   High                               Very low

Recent events in the USA may have changed your perception, at least with respect to microbial contamination.

Time for red faces? Perhaps raw milk is not all it's cracked up to be.

2010-11-08T16:27:00.000-08:00

The last time I wrote a blog on raw milk, I received "fan mail" accusing me of being sensationalist and closed minded. At risk of more unflattering comments, here is another post on the subject.

Proponents of raw milk consumption have long claimed health benefits of raw milk and products made from it. One of those claims is that lactose intolerant individuals, who don't produce sufficient lactase in the small intestine, suffer reduced symptoms if they consume raw milk, rather than pasteurised.

Stanford School of Medicine recently conducted a study of self-reported lactose intolerant individuals, who were given raw milk, pasteurised milk and soy milk in a randomized, double-blind, three-way crossover trial. This classic experimental design removes bias in experimenters and subjects. If lactose intolerant individuals consume lactose (the sugar found in milk) they cannot break it down to glucose and galactose. Anaerobic bacteria in the colon grow on the lactose and produce hydrogen, some of which enters the bloodstream and appears in exhaled breath.

The participants were tested for exhaled hydrogen on the first and last days of each 8-day exposure period. There was no statistically significant difference between consumption of raw or pasteurised milk, but soy milk resulted in much smaller amounts of breath hydrogen. Similarly, the symptoms reported - flatulence, abdominal cramping and diarrhoea - were the same for both raw and pasteurised milk.

The researchers reported that the results from their work, collected under standardised, controlled conditions, did not support the claim that, with respect to lactose intolerance, raw milk has benefits over pasteurised milk.

Meanwhile, raw milk and raw milk products continue to be linked with outbreaks of Escherichia coli and Listeria diseases

http://www.marlerblog.com/legal-cases/e-coli-and-listeria-in-raw-milk-and-cheese---growth-sectors-at-marler-clark/

Irritable Bowel Syndrome - good site

2010-10-17T15:52:00.000-07:00

Irritable Bowel Syndrome (IBS) is still something of a mystery, but those who suffer from it are in no doubt that it is real. Many explanations have been advanced for it and various remedies have been proposed.

Though the subject is not really on the topic of safe food, I thought it would be good to provide readers with a link to a new website from the Marler Clark stable. The website is just about to go live, but here is an introductory link:

http://www.foodpoisonjournal.com/2010/10/articles/foodborne-illness-outbreaks/irritable-bowel-syndrome-and-postinfectious-ibs/index.html

Where's my PhD student?

2010-09-26T19:16:00.000-07:00

I had a scheduled meeting with my PhD student this morning, but she didn't turn up. I got a somewhat graphic text message, saying that she had food poisoning. It seems that she, her partner and two friends went out for dinner in a restaurant in Auckland on Saturday. They all appear to have food poisoning.

Of course, this doesn't prove that the restaurant was responsible. Indeed, her description of the symptoms and time of onset make me wonder if another common source was involved.

However, a TVNZ One News investigation shows that on average, one Auckland food establishment per week has been shut down this year because of safety or cleanliness violations.

http://tvnz.co.nz/health-news/shocking-food-hygiene-figures-auckland-3800902

An Auckland City Council Environmental Health spokesperson said that the increase in closures was a result of tougher action by health inspectors in response to unsatisfactory performance and suggested that this was partly because of the economic recession - companies were selling food that would previously have been thrown out.

A disturbing statistic given in the TVNZ report is that over 100 restaurants and cafes are still operating, despite poor hygiene ratings, though to be fair, businesses are given the opportunity to clean up their act before being closed down if they don't improve.

This report begs the question "If inspectors had previously found unsatisfactory conditions in food outlets, why didn't they close them down at the time? What has changed in the requirements to serve wholesome, safe food in clean premises?"

To test, or not to test – that is the question (with apologies to Shakespeare).

2010-09-22T22:47:00.000-07:00

I had intended to write my next blog article on the latest information on Campylobacter in New Zealand. However, in view of the continuing Salmonella-in-eggs problem in the USA and yet another recall in New York State of ground beef owing to the detection of Salmonella, I decided to write about product testing and the alternatives.

It had been suggested that the feed was the source of Salmonella that infected the Wright County Egg Co. Reporting in the Wall Street Journal last week, Alicia Mundy and Bill Tomson wrote that the Food and Drug Administration had failed to detect Salmonella at the premises of the suppliers of the feed:

http://online.wsj.com/article/SB10001424052748704394704575496191032884412.html

Officials warned that the investigation was continuing, but from my point of view, the fact that Salmonella was detected in the Wright County Egg Co. farm(s) on 426 occasions from 2008 to present is a pointer to the farms at least having some responsibility.

Testing of products, be they eggs, steaks or lettuces, can potentially detect Salmonella and other pathogenic bacteria, such as Escherichia coli O157:H7, allowing us to reject the lot. Unfortunately, testing doesn’t guarantee that we will detect Salmonella. In all sampling plans that I am aware of, detection of Salmonella in the sample is cause for rejection. Under the ICMSF 2-class attribute sampling plan nomenclature, ‘n’ is the number of samples to be taken from a lot, ‘c’ is the number of failures permitted and ‘m’ is the threshold above which the sample fails. Thus for Salmonella testing, c = 0 and m = 0. What number of samples should we take?

Statistics show us that when the frequency of contamination in the lot is 1 in 1000, setting c = 0 we would need to examine 2995 samples to achieve 95% confidence in detecting the defective sample; that is, we would still have a 5% chance of accepting a contaminated lot.

Put another way, extensive testing is prohibitively expensive, and many sampling plans call for only 5 samples to be taken from a lot. Even with 40% of the lot being defective, we would still accept the lot about 8% of the time.

So, testing seems a bit unreliable. Is there a better way? Well, yes there is. It’s called HACCP (Hazard Analysis Critical Control Points) and it came out of the space programme, developed initially as the Modes of Failure Programme by the Natick laboratory and then by The Pilsbury Corporation. Without going into detail on this occasion, it involves looking at the ingredients, the process and the processing facilities and looking for every way the food might become unsafe. These aspects are eliminated where possible and those hazards that cannot be eliminated are controlled by keeping tight control over Critical Control Points, such as cooking operations.

The hazard analysis can then be used to develop a Food Safety Programme for the factory. The factory runs the process according to this programme and monitors the CCPs and keeps accurate records of the entire process. There is then no need for end product testing – if the process is under control, safe food will be produced. Regulatory monitoring becomes a matter of checking the records and auditing the programme on a regular basis. This is a really good system and in a perfect world, it would work perfectly.

The problem with this approach is that the regulators need to have enough staff to do the inspections and the companies running the factory have to obey the rules, keep accurate records and come clean the minute something goes wrong. Companies must want to produce safe food, rather than just make money.

It is very sad that in many of the recent food poisoning outbreaks, it has eventually been shown that companies falsified records, while supposedly independent inspections were at best inadequate and at worst negligent and corrupt.

In this environment, the regulators need more staff, better legislation and more powers to shut down unsafe operations. I have watched in horror as one outbreak after another has resulted in severe injury to some consumers, massive food recalls and in some cases permanent shutdown of factories and wondered, “Where will it all end? Will there be any food manufacturers left in business? Will testing requirements become so onerous that food becomes ridiculously expensive?”

I don’t think there is an easy solution, but until the cowboys have all gone, I see no alternative to better legislation, more truly independent inspection, more frequent testing of product and full traceability of raw materials and finished products.

Would you like your Salmonella over easy or sunny side up, sir?

2010-08-20T23:38:00.000-07:00

550,000,000 eggs have now been withdrawn from the market in two recalls in USA.

380m eggs were recalled early last week by Wright County Egg and now 170m eggs have been recalled by Hillandale Farms of Iowa. Eggs from both companies have been linked with salmonellosis affecting at least 1700 people.

Salmonella is a bacterium found in the gut of man, animals and birds. It causes nausea, vomiting, abdominal pain and diarrhoea that may last for several days and can be fatal in the very young or elderly. It is usually contracted by ingestion of faecally contaminated food, though this is not the only route of infection. The disease is described as a “food borne infection”, because after ingestion of infected food, the bacteria grow in the gut, causing the symptoms, which appear 12 to 14 hours after ingestion.

Why have so many eggs been withdrawn? I think it’s probably because of the way the regulations governing poultry farming in the US are written. As I understand it, testing is conducted under the FDA “Egg Rule” -Environmental Testing for Salmonella Enteritidis (21 CFR 118.5). Samples are taken from the environment to determine if S. Enteritidis is present, because this is an indicator of the effectiveness of the SE control plan. The pullet environment is tested when the pullets are 14 – 16 weeks old and in addition, the environment in each poultry house is tested when any group of laying hens reaches 40 – 45 weeks of age.

If rodents, birds or insects introduce Salmonella to the poultry house, between testing times, the infection could spread rapidly throughout the flock and eggs could be produced from infected hens. Hens can become infected internally and eggs can be infected before the shell is formed. There is no way to tell if an egg is infected with Salmonella, other than cracking it and culturing the contents. Eggs are required to be tested only when an environmental sample is shown to be positive. So the huge recall is to ensure that all potentially contaminated eggs are removed from the market place and homes.

How can consumers protect themselves from contracting salmonellosis? The most obvious precautions are the proper refrigerated storage and cooking of eggs, washing hands after handling eggs and avoidance of products containing raw eggs, such as home made ice cream and mayonnaise, or coddled eggs. If you have eggs subject to the recall, dispose of them or return them to the retailer for a refund.

Eggs in New Zealand are unlikely to contain Salmonella. In the next posting, I’ll discuss this and the latest on Campylobacter in New Zealand.

Just a thought: How are they going to dispose of 550m eggs? At 60g (about 2 ounces) each, that is about 33,000 tonnes (36,376 US tons) of eggs.

More on Salt in Foods

2010-08-12T21:49:00.000-07:00

It’s generally accepted that we eat too much salt in New Zealand – up to 150% of the maximum recommended intake (see Sodium in Food, 13 July 2010). Excessive consumption of sodium raises blood pressure and may increase the risk of cardiovascular disease. Bread is the greatest contributor to our sodium intake, followed by sausages and processed meats.

One of the concerns of manufacturers of foods that contain added salt is that the consumer will detect the change if salt content is reduced and refuse to buy that brand.

In 2003, I took part in a trial in which we tested three commercially baked breads with varying levels of salt, from the standard content at that time of 550 mg/100g, 5% reduction (530 mg/100g) and 10% reduction (490mg/100g). We performed controlled trials in which 60 consumers were given three samples - two identical and one different - and asked to pick the odd one out. This is called a triangle test. Twenty eight percent of the panellists correctly identified the 5% reduced sample and 37% identified the 10% reduced salt bread. This relatively small trial showed that these differences in perception of salt content were not statistically different i.e. that the consumers could not detect the lowered salt breads. Recent figures show that some breads now have 20% less salt than equivalent products in 2003.

As I wrote in “Sodium in Food”, July 2010, sodium chloride has many functions in foods besides flavouring. What are the alternatives to salt? We can replace some sodium with other ions, such as potassium, magnesium and calcium. We can purchase reduced sodium table salt, though the UK Food Standards Agency does not recommend the use of salt substitutes, as they don’t reduce consumers’ taste for salt. Replacement of 40% of sodium by potassium in manufactured foods may result in detectable flavour changes and there may be problems for people with kidney conditions. We could use other preservatives, but consumers have been fed the line that preservatives are bad for them, so there is likely to be resistance to this approach. We could target other sources of sodium in the diet, such as monosodium glutamate (MSG, a flavour enhancer), or water binding agents, such as sodium tripolyphosphate.

How will we know if reducing salt in our food will result in safe food? We can conduct computer-based modelling experiments, using the vast resources of microbial growth models stored in databases. Some of these databases are freely available and allow us to predict such things as “time to spoil” or “time to toxicity” or simply “how long will it take this initial level of contamination to grow to an unacceptable population?” We can vary the formulation of the food and run the model again to see how it performs. In a matter of minutes, we can do extensive trials of alternative formulations.

Unfortunately, these models are not real foods. Once we have modelled the likely shelf life etc. we have to make samples and test them under normal storage and abuse conditions. This is not straightforward and can be very costly. The likelihood therefore is that we will not see rapid reductions in salt content of our manufactured foods, but rather a progressive reduction, as was the case with bread. We can, however, make a start on personal salt intake reduction by using other seasonings and spices in our homes.

The joy of cleaning (yeah, right)

2010-08-07T18:57:00.000-07:00

I was recently interviewed for a forthcoming television programme dealing with mould in the bathroom. I decided to brush up on my knowledge of cleaning chemicals to try to avoid getting caught flat-footed by the interviewer. When you really get into it, the science behind modern cleaning technologies is quite fascinating and more complex than you might expect.

My research team specialises in the study of biofilms. These accumulations of microorganisms and their sticky products on surfaces are extremely hard to clean. Since I have mentioned biofilms in earlier posts, I thought that it might be time to examine them in more detail here.

Pasteur and Koch laid the foundations of modern microbiology by culturing bacteria on solid media in pure culture. This development enabled microbiologists to study individual strains of bacteria without the interference of other types and we have continued to use their techniques. However, it is now generally accepted that bacteria grow preferentially as biofilms – complex communities growing on a surface and surrounded by polysaccharide slime known as glycocalyx. Among other things, this glycocalyx gives the bacteria protection from cleaning agents. Failure to take account of this when formulating cleaners and disinfectants can result in incomplete removal of the film. This is particularly important when the surface is a piece of food processing equipment.

Go and have a look at your beautiful stainless steel kitchen sink or the shower tray. They look perfectly smooth and should be easy to clean. However, when we use a scanning electron microscope to see the surface on the same scale as bacteria, it is clear that the surface is anything but smooth (see first figure). Bacteria can get down into the troughs between the grain boundaries and it’s obvious that getting them out of there is going to be difficult. The difficulty of cleaning is made worse if the bacteria are left to grow long enough to form a proper biofilm. The bacteria produce a sticky mixture of polysaccharides, which glues them to the surface and attracts other bacteria and traps food particles (see image at right).

When we buy a cleaning product from the supermarket, we are buying a carefully formulated mixture of chemicals that has a number of functions: it must bring the chemicals into close contact with the biofilm; proteins, carbohydrates and fats must be solubilised or suspended so that they can be rinsed away; for domestic cleaning it is also desirable that the cleaning product should kill bacteria. (In industrial cleaning, a separate sanitiser is usually applied after cleaning).

To satisfy these requirements, most cleaning products contain a surfactant to break down the surface tension of water (to make it “wetter”) and an alkali to solubilise proteins and fats. Sometimes an acid is used to remove scale deposits. Industrial cleaners for food processing equipment often also contain hypochlorite, which releases hypochlorous acid and ultimately an oxygen radical, both of which are strong oxidising agents that can break down dirt. Because of the potential danger to consumers, domestic cleaning products are usually much less alkaline and generally weaker than industrial cleaners.

I am often asked whether there is an alternative to the “harsh chemicals” used in cleaning products. Well, there are so-called “green cleaners” derived from plant materials, but the principles behind the formulations are the same – combination of surfactant such as an alkyl polyglucoside from palm and coconut, with citric acid and a solvent, D-limonene, from citrus skins. I have heard of white vinegar being used to remove bathroom mould instead of the chlorine-based cleaners. However, even the proponents of such substitutions admit that a lot more effort is required to remove the mould and that it soon comes back. This is partly because vinegar has no surfactant properties.

Successful cleaning requires four things: the right concentration of cleaning product, suitable temperature, mechanical energy (“elbow grease”) and sufficient time for the chemicals to penetrate the dirt and destroy bacteria. The best way to ensure that cleaning is successful is to follow the instructions on the label – the manufacturer has formulated and tested the product to be used in a certain way.

If done correctly, cleaning will remove biofilms from stainless steel. The two images at left show a piece of stainless steel before and after cleaning. The bacteria were stained with a fluorescent dye and observed under UV light in a fluorescence microscope.

However, a successful cleaning operation is only a temporary fix and regular cleaning is essential to prevent biofilms from forming. Like death and taxes, it’s not much fun and there’s really no getting away from having to clean.

Credits for photographs provided by my research group:
First image by Steve Flint and Doug Hopcroft; Second image by Shanthi Parkar and Doug Hopcroft; Third and Fourth images by Shanthi Parkar.

(The description given above is still a simplification of cleaning technology. I have tried to capture just the essentials of the process and the cleaning products).

Sodium in food

2010-07-13T22:12:00.000-07:00

Most people like to have salt on their food. In mediaeval England, salt was expensive and only the nobility could afford it, as it was made by evaporating salt water over a fire. The salt was placed in the middle of the high table; the commoners sat at lower trestle tables and did not have access to the salt. Thus they were "below the salt" and this came to be an indication of rank.

Around 1650, rock salt was mined in Cheshire and salt became more readily available. The connotation of the value of salt remains, however, in expressions like "He's worthy of his salt".

These days, we probably have too much salt in our diets. In New Zealand, for instance, we consume around 150% of the recommended upper intake level. Much of this intake is involuntary - manufacturers add it to foods including bread, sausages and pies. The recent television series "Master Chef" had the judges saying repeatedly "Don't forget the seasonings", meaning not just herbs and spices, but also salt.

So, should we just ban salt in food and let individuals add salt to taste?

The answer may surprise some readers. Salt (sodium chloride) contributes to the safety of food and is essential for developing texture and flavour in processed meats. It helps to bind proteins, improving texture; it increases water binding capacity of proteins, also contributing to texture and assists in stabilising meat batters by improving fat binding. It also decreases fluid loss in vacuum-packed, thermally processed products.

Not only that - salt improves safety and shelf life by inhibiting the growth of bacteria, though relatively high levels are required if salt is used alone. It helps to reduce the water activity^* of the food, making it more difficult for bacteria to grow. That's why salted beef and pork were carried on long sea voyages - the meat was preserved.

Stringer and Pin (Institute of Food Research, Norwich, UK) have noted that "There is scope to reduce salt in foods. However, as salt influences bacterial growth, survival and recovery after adverse treatments, reducing salt in foods will have consequences for food safety that must be considered". These researchers used predictive models to show that reducing sodium content from 1.5g/100g to 0.76g/100g food allowed a much greater growth rate of certain foodborne pathogens. This could be acceptable, but other preservative mechanisms would need to be put in place. For example, other preservatives might be added at low levels and refrigeration might be necessary. Above all, reducing salt content would require even stricter adherence to good manufacturing practices, particularly with respect to plant and operator hygiene.

I'll write more on sodium in food in a follow-up posting.

* See the end of "Free Choice or Safety of the Population" in this blog for an explanation of water activity.

Old lessons not learned - Re-post

2010-06-27T15:06:00.000-07:00

I have just returned from a meeting of food experts in Wageningen, Holland. One evening, we were taken to the Zoo in Arnhem. This fantastic place has a number of indoor environments, such as a jungle, ocean, desert and a restaurant.

After the visit, we had a meal in the somewhat inappropriately named Burgers Zoo Restaurant. A feature of this is the do-it-yourself barbeque. This ingenious device is like the continuous toasters you see in some hotel dining rooms – the food is placed on a continuous belt grill and passes over heated briquettes. Diners select their meats and salads from the large range set out on side tables.

Not having completely switched out of professional mode, I watched my fellow foodies to see how they would cope. I guess I should not have been surprised to see several of them take their raw meats and salads onto a single plate. They cooked the meats and then put them back onto the same plate! Nobody took fresh tongs or heated the ones used to put the meat on the grill.

Clearly, not all the participants were experts in food safety, but I had hoped that they would know about basic food safety rules – cooked food should NEVER be put on a plate that has held uncooked meat and cross contamination of salads from raw meats must be avoided. When I pointed out their mistake to a couple of my colleagues, they understood, but still didn’t know what to do about it.

At the other end of the scale, one young lady expressed concern as to whether she had cooked her steak sufficiently and was she at risk of food poisoning? In my opinion, her meat was over-cooked, but it would certainly have been safe to eat. Raw steaks from a healthy animal are essentially sterile on the inside, so they can be made safe by cooking the outside properly. (Minced or ground meat has had the outside mixed into the inside, so cannot safely be eaten rare). She expressed the view that barbequing was a bloke’s job, but I wonder if it should be left to food microbiologists?

Safe Food has a following!

2010-05-28T21:52:00.000-07:00

I noticed today that someone has become a Follower of Safe Food. Thanks, Kim.

You can keep track of new posts if you click the "Follow" tag next to the search box at the top of Safe Food. Your picture, contact details and other followings will appear in my Blogger Dashboard, but currently will not appear on the page. If you have a Blogger Dashboard, you can set up a reading list and new postings will appear there.

You can also subscribe to Safe Food by clicking on the RSS symbol at the right hand end of your browser address bar. You will receive an e-mail notification each time I add a new post.

You can search Safe Food by entering Label terms into the search box in the page header. You will find an alphabetical list of all the Labels I have used under the Blog Archive.

You will also find under the Labels list a few links to other food safety sites that I read.

I hope that these enhancements will help you to benefit from reading Safe Food.

Guest Editorial - Additives in New Zealand Foods

2010-05-21T17:33:00.000-07:00

This blog has not been updated for some time, mainly because we have been hard at work studying the growth of Cronobacter sakazakii. This work has now been submitted for publication and I have time to write more articles. Some of our work on C. sakazakii will appear in a later post.

To get us off to a good start, here is a guest article, written by one of my colleagues, Associate Professor Owen Young of Auckland University of Technology:

Food Additives in New Zealand

I recently had AUT University students systematically survey packaged food labels in Auckland supermarkets for health claims. These could be real (e.g. ‘if you eat this food your cholesterol will be lower’), or implied (e.g. ‘contains no additives’, ‘all natural ingredients’ etc.).

Over 30% of products surveyed had a ‘fat’ claim such as ‘lo fat’, ‘low in saturated fat’, or ‘98% fat-free’. Arguably these claims could be useful to a buyer seeking to control their weight, but overlooks the fact that total energy intake is really what matters for obesity. Fat is not the only beast with calories.

But of more interest to me were the claims for avoiding Public Enemy Numbers 1, 2 and 3: artificial colours (28% with claims), preservatives and artificial flavours (both 24%). Anyone would think these things were dangerous. But are they dangerous in the way they are used in foods?

Take the yellow food colouring tartrazine for example. Googling ‘tartrazine allergy’ will score you thousands of hits. On the face of it you would have to wonder why Food Standards Australia New Zealand (FSANZ) allows artificial food colouring to be used at all. The reason is because the evidence for adverse effects from these colours is so flimsy as to be laughable. Colours have been used in foods for decades with no adverse effects. So why are some colours banned in certain countries? The reason is that pressure groups have been so strident that it becomes politically expedient to roll over and appease the activists.

Preservatives are sometimes put in prepared foods to minimise the growth of bacteria. These bacteria can either degrade the food, but be otherwise harmless, or they can be pathogens. At best the latter can make you sick and at worst can kill you. The maximum quantity of preservative added is typically hundreds of times lower that the amounts required to show any kind of response in humans. Preservatives have excellent safety records, and that is why FSANZ allows their use. You would have to wonder about a food manufacturer who neglected to add a preservative to a susceptible food. Such action should be viewed as callous indifference to your health.

The so-called artificial flavour that gets most bad press is MSG, monosodium glutamate. Ostensibly MSG is responsible for the Chinese restaurant syndrome with its claimed headache, flushing, and tingling symptoms. But MSG has been used extensively in Asian cooking for donkey’s years. If it’s so bad, why doesn’t everyone in Asia have a headache? The truth is that it is not bad for you.

Very many common foods have high concentrations of MSG, but no one complains about MSG in cheese, soy sauce, walnuts and broccoli, and a host of other foods. Chinese restaurant syndrome is nothing but an enduring urban myth. So why does MSG have to be declared on labels? One reason is that regulators are simply responding to activist demands. Any hint of a potential problem is dealt with by a label declaration that presumably implies that the additive is a risk and so feeds the myth.

What can or cannot be added to food in New Zealand is governed by FSANZ’s Food Code, which is online for all to read. One guiding principle is you can put additives into foods only where allowed and where needed – up to a specified limit – and crucially, only enough to achieve the required result. You cannot add stuff just for the hell of it, and indeed why would you? Additives cost money and there is often no need for them.

Take beer for example. Current advertisements frequently have an ‘all natural ingredients’ claim – whatever ‘natural’ means – and a ‘no preservatives added’ claim. The Food Code allows only one preservative in beer, sulphur dioxide, but it is seldom added because beer, by its very nature, keeps well without preservatives. Similarly, preservatives are not added to breakfast cereals because they are not needed in these dried foods.

The Food Code is thus a very conservative document, making New Zealand food supplies among the safest in the world.

So feel free to ignore the implied health claims that are built on the flimsiest of evidence, and are used to part you and your money through a fear of chemicals – chemophobia (n): an irrational fear of chemicals, particularly those man-made.

Associate Professor Owen Young is Academic Leader, Food Science, AUT University, Auckland

It’s not quite about food safety…

2009-12-18T18:57:00.001-08:00

Recently I was asked by a reporter to test magazines found in doctors’ waiting rooms for presence of pathogens. She wanted to do a story about the risks of going to the GP. I wasn’t sure what to expect, but asked her to collect a range of magazines from various waiting rooms. She brought me ten glossy or super glossy magazines covering popular women’s and men’s titles.

Each magazine was opened randomly and two pieces of the right hand page were cut aseptically, using sterile scissors. Each piece was 100mm x 100mm; one piece was cut from the top right, the other from the bottom right. This was to increase the chance of sampling the area most handled by readers.

The pieces of paper were transferred to a sterile bag with sterile diluent and massaged thoroughly by hand and then for two minutes in a machine called a Stomacher. I transferred samples onto agar plates that would enable me to assess general microbial contamination, faecal bacteria and Staphylococcus.

After incubation, I examined the plates, looking for typical bacterial colonies. The levels of contamination on all media were low. The limit of detection in this analysis was 3.7 colony forming units/10 cm². In the food industry, a count of less than about 100 cfu/cm² is considered acceptable, though the count on food contact surfaces at the start of food processing should be close to zero. Thus, the analysis I used was sufficiently sensitive to indicate whether the magazines were microbiologically hazardous with respect to Staphylococcus and faecal bacteria.

Staphylococcus is typically found on the skin and can be transferred to food and there produce enterotoxin, which causes food poisoning when we eat the contaminated food. It is unlikely that the low levels of S. aureus detected in this work would lead to significant transfer between readers. No typical colonies of faecal coliforms were detected, suggesting that there were no, or very low numbers of faecal bacteria on the magazines and hence that the likelihood of faecal contamination of the pages was also low.

All of the samples were printed on glossy paper, which doesn’t absorb water, a fact I confirmed by measuring the water activity* of the samples. There was thus no opportunity for bacteria to grow on the pages and in fact, they may have died off reasonably quickly.

One thing I should point out is that it is not possible by any simple analysis to detect viruses, so the work done here doesn’t completely rule out contamination by viruses of upper respiratory tract or gastrointestinal tract origin. Some, such as the Norwalk virus that causes gastroenteritis, can survive on surfaces for long periods.

I conclude from this cursory examination that, with the possible exception of viruses, the pages of the magazines were relatively free of pathogens. Handling the magazines is therefore relatively hazard free. However, as always, it would be advisable to wash or sanitise hands before consuming foods, snacks or sweets after visiting the surgery.

Have a happy and safe Christmas, everyone. Make sure your Christmas fare and BBQs are safe.

* For a description of water activity see:

http://foodsafetywithjaybee.blogspot.com/2007/06/free-choice-or-safety-of-population.html

Raw milk and people with influence

2009-12-02T19:05:00.000-08:00

It’s happened again! Bill Marler quotes a Washington State Department of Agriculture News Release, reporting that three recent Escherichia coli infections in Washington have been linked to drinking raw, unpasteurised milk. The Washington state departments of Health and Agriculture have put out new warnings about the risks of consuming unpasteurised milk and milk products.

All the patients involved have reported drinking raw milk from the same supplier. Though no E. coli have been found in the most recent batch of product tested, the Washington State Department of Agriculture did find in the dairy the same strain involved in one of the illnesses.
Bill Marler, Doug Powell and I have all written on many occasions about the hazards of consuming raw milk. Doug has emphasized that personal freedom is all very fine, but young children cannot exercise freedom of choice. They are often the ones made ill by bacteria carried in raw milk. If you think that we are a bit over the top on this issue, have a look at the You Tube clip of Barb Kowalcyk talking about her son, Kevin, who contracted haemorrhagic E. coli infection.

http://www.marlerblog.com/2009/12/articles/legal-cases/perfectly-healthy-to-dead-in-twelve-days-hemolytic-uremic-syndrome/

A few days ago, Tamati Coffey was shown on TVNZ’s “Breakfast” programme milking a cow and then drinking the milk. No real problem there. The show’s hosts, Pippa Wetzell and Paul Henry then discussed the merits of drinking raw milk. Typically, Paul reckoned he wouldn’t touch the stuff, but I was surprised when Pippa, who recently had a new baby, argued that drinking raw milk is good for you. Many people watch this programme every day and there must be a proportion of those who are mothers of young children. Judging by the daily feedback, viewers hang on every word the presenters utter. I have to admit that I too enjoy the quick repartee of Paul and Pippa, but her throwaway line could easily influence parents to feed raw milk products to their children, with potentially disastrous consequences.

Perhaps television presenters should be a bit more careful when it comes to expressing views on the safety of foods – they are not trained in food safety. As they said in the post-war years when I was a lad “Careless talk costs lives”. It’s just as true today.

New technology to double avocado shelf life: NZL FOODweek Online Main Features Page

2009-10-20T18:32:00.000-07:00

New Zealand FOODweek Online published an article on high pressure processing (HPP) of avocado to extend shelf life. The link is shown below:

New technology to double avocado shelf life: NZL FOODweek Online Main Features Page

HPP has been used for some time, particularly in Japan for cold pasteurisation. In a future blog article, I will write about HPP and explain how it works and how it can be applied to foods.

“The Law is an Ass” – with apologies to Mr. Dickens.

2009-10-08T02:01:00.000-07:00

In the last week, the Far North District Council in New Zealand has enforced the law and required community members to desist from cooking pickles and jams and selling them through a Hospice Shop. Over the years, these wonderful people have raised around $5000 for the hospice funds each year.

It appears that the District Council received a complaint that the goods were being produced in private kitchens. Under the Food Hygiene Regulations, the council was then obliged to investigate. The regulations specify that production of foods for public consumption may be conducted in unregistered premises only on special occasions.

This situation crops up more than you might expect. About 25 years ago, when my children were small, our country school raised significant amounts of money by pizza drives. About three times a year, the Parents Association purchased commercially made pizza bases and assembled pizzas for sale. The council received a complaint from a commercial pizza parlour that this was unfair competition, since the school did not have a registered premises and therefore had lower costs. We were able to comply with the regulations by specifying the number of times a year our Occasional Food Premises would be used and by registering a relatively simple Food Safety Programme.

To give credit where it is due, the Far North DC and the New Zealand Food Safety Authority (NZFSA) are looking at ways the volunteer cooks can continue to produce their foods. Their home kitchens are not registered premises and it is not practical for the volunteers to set up a separate kitchen. I’m looking forward to seeing how the Authority gets around its own antiquated regulations.

However, what is the real risk? The products are essentially heated, acid foods – jams are made from acidic fruit and have a low water activity*, so the most likely microbial spoilage – if there were to be any – would be mould growth, which would be apparent to the consumer. Pickles are acidified foods and the low pH has the same effect, preventing the growth of pathogens. So the microbiological risk to consumers is low. Fruit cakes and similar baked goods are not hazardous either. Obviously, good hygiene in production and handling of all these foods is essential and potential contamination with cleaning chemicals etc. must be prevented.

What are the most hazardous foods on sale today? According to the Centre for Science in the Public Interest, these are leafy greens, with 363 outbreaks (13,568 reported cases of illness); eggs (11,163), tuna (2341), oysters (3409), potatoes (3659), cheese (2761), ice cream (2594), tomatoes (3292), sprouts (2022) and berries (3397). These are listed in order of outbreaks. Notice that jams, pickles and cakes don’t figure in the statistics.

Back in the Far North, everyone is looking to see this resolved soon, so that the volunteers can resume their work for the hospice. The Food Hygiene Regulations are due for replacement with a new Food Act that will shift the emphasis to risk assessment of food processing operations.

As the Assistant Director of NZFSA apparently said, “The law isn't based on common sense and we're looking to improve things."

* See the end of "Free Choice or Safety of the Population" for an explanation of water activity.

A note on comments to this blog

2009-08-20T16:37:00.000-07:00

Occasionally (sadly not very frequently) one of you readers posts a comment, often on a blog article I wrote months earlier. Your comments are moderated and appear under the relevant article.

Comments come to my private e-mail address for moderation and are anonymous, so I can reply only by posting another comment, which again appears under the relevant article.

If you have commented, please look at the article comments for my response. If you want me to reply directly, please use my e-mail address you see in the blog header.

John

Follow-up on canned food production.

2009-06-28T20:48:00.000-07:00

In the last posting, I was writing about canned foods and the consequences of their going out of their “best before” date.

I was confident that the young man in question was not at risk. Here’s why (sorry for the lecture).

Canned foods have been made commercially in significant amounts since about 1874, when Schriver invented the closed kettle – a device that allowed processing at temperatures above that of boiling water. Before that, commercial production was carried out, but the products sometimes spoiled. (We tend to forget that up until 1860 it was not known that bacteria cause food spoilage. The spoilage was almost certainly the result of failing to deliver a harsh enough heat process to destroy bacterial spores. Some spores can survive more than 4 hours in boiling water).

In all that time, manufacturers have developed reliable processes by experience. Scientists have been able to explain why the heat treatments work and thus design new processes with confidence. In the case of low acid canned foods (LACF) we have to rely totally on the process. We cannot test for safety.

You might ask “Why would it be difficult?” The problem is that we demand a high level of security i.e. we set the acceptable risk of food poisoning from LACF as around 1 in a billion (I mean a million million) i.e. only one can in a billion would contain a viable spore. There is no testing regime that could detect the presence of viable spores even ten times that limit.

The LACF process is designed, using a combination of knowledge of the type of microorganisms likely to be found in the food (and able to grow under those conditions) and the measured death rate of these bacteria, to calculate a process that will guarantee to destroy them. In the case of LACF, we are interested in a process that will destroy the heat resistant spores of Clostridium botulinum, leaving only one survivor in a billion. We call this a "12D" or 12 decimal reduction process. (See also the previous posting).

So when my reader contacted me and asked me to test the food for her, I knew that it was pretty much pointless. If the food had been processed properly and the seal remained unbroken, then she could rely on the food being safe for her son.

Do consumers understand “Use-by” and “Best-before” dates?

2009-06-25T14:31:00.000-07:00

I think that many consumers don't understand these package marks.

I recently received a message from a very distressed reader. She'll recognise herself, but I'm sure she won't mind my writing this.

The reader had a 16-month-old son and had fed him a jar of organic apple, pear, blueberry and blackberry with vitamin C. The young man had eaten it all and was apparently bouncing around, as 16-month-olds tend to do. The jar and contents appeared normal, with a suitable vacuum in the headspace.

After the meal was over, the mother looked at the jar and found the “best before date was 29th July 2008!” (her exclamation mark). She went on: “I am very concerned that he could get Botulism from this - is there a way that I could get the remains of the food in the jar tested to make sure that he is not in any danger? Please, I am happy to pay for this and your time.

“I have spoken to a few people and they have all said that we will have to wait the 10 days to be on the safe side. Is there anything else I can do to protect my son? or help to prevent anything really nasty making him sick from this?”

This mother was obviously very frightened. Her concern was triggered by the best before date, which is an advisory to the consumer about quality. Chemical changes can occur slowly in cans or jars of food during storage. These changes may be accelerated if the food is exposed to sunlight or high temperatures. These changes may make the food less appetising, such as giving a "cardboardy" or flat, oxidized taste. The changes are not harmful. If the food is outside the Best Before date, it does not necessarily indicate that it is unsafe to eat, though that might be the case with something like ham or egg salad, which are much more perishable.

I didn’t have any further information on the product, but would expect that it would have been processed either as an acid food (pH less than 4.6) and pasteurised, perhaps hot-filled, or processed as a low acid food (pH above 4.6) and thus be given a 12D process (sterilised). In either case, Clostridium botulinum toxin would not be produced. Any changes occurring after the best before date would be quality deterioration only, not safety issues. There are several other points to come out of this discussion, but I'll cover them in a future posting.

Extrapolating from this, it is probable that consumers and perhaps retailers don’t fully understand the significance of “use-by” dates. I have certainly seen products in supermarket display cabinets with the original “use-by” date covered with a second label bearing a later date. The latter is illegal in New Zealand.*

And the boy? I had a message from his Mum today - this is the 11th day since he ate the food, which had actually been made in 2006. He didn't get sick and is now toddling around the home at high speed. Well, some food stories have happy endings!

* You can find an article "Date Marking - Standard 1.2.5" on the NZFSA website at www.nzfsa.govt.nz/

Don’t read this if you have a weak stomach

2009-05-23T23:52:00.000-07:00

The reason for the title will become apparent later on!

People who have an opportunity to influence the public have a duty to make sure they know what they are talking about and to think about the consequences of their comments.

Last week, popular TVNZ breakfast show host Paul Henry was talking about the state of cleanliness in public toilets. The breakfast show is a mixture of news, views and entertainment and Paul made a meal (if you’ll pardon the pun) of the issue, drawing out as much toilet humour as possible. Unfortunately, he also claimed that washing your hands in a public convenience would result in your hands being more contaminated than if you had not bothered.

This is hard to stomach. Certainly, taps and door handles may be contaminated, often with faecal bacteria and it may be that soap and soap dispensers are also contaminated. However, I find it difficult to accept that not washing hands is better than washing.

If you didn’t take the earlier warning, now is the time to quit reading.

If you have wiped your backside with toilet tissue, then the chances are that your fingers are contaminated with faecal bacteria and viruses. Way back when I started teaching food microbiology, I used to run an exercise with my students. They took various numbers of sheets of toilet tissue and placed them over a finger end, which they then gently wiped across a Petri dish of indicator bacteria. These, as it happens, were Escherichia coli, the bacteria always present in the gut. These bacteria have the ability to produce a green metallic sheen when they grow on an agar called Eosine Methylene Blue. Since they occur only in the gut, we should not normally expect to find them on our hands, except for the obvious reason. After the wiping phase of the experiment, the tissue was discarded and the same finger pressed onto the EMB agar, which was then incubated overnight. The students then washed their hands and dried them before making a further agar impression.

The students were usually horrified to discover that even when using 6 sheets of 2-ply toilet tissue, their finger impressions often grew bacterial colonies with a green metallic sheen. Now, not to put too fine a point on it, 6 sheets is an almost unmanageable wad of paper! Washing usually removed all the bacteria, but only if soap and warm water were used.

There are several messages here.
• No matter how much tissue you use, you can’t be sure that you won’t have faecal bacteria and viruses on your fingers.
• Washing your hands with soap and then drying them will remove most of the bacteria

Unfortunately, when you turn on the tap with contaminated hands, they will transfer bacteria and viruses to the tap. After you have washed, you recontaminate your hands when you turn the tap off. That’s why in hospitals and laboratories the taps have long handles that can be operated with wrists or forearms, or are operated by foot pedals or infra-red sensors. These days, many washroom taps have press buttons that allow the water to run for only 30 seconds or so and don’t need to be turned off.

So what can you do?
• Turn the tap on with your wrist
• Wash your hands thoroughly with soap (sing “Happy birthday" to yourself twice to ensure you wash for long enough)
• Thoroughly dry your hands on a paper towel and then use it to turn the tap off
• If the washroom has blower hand dryers, be careful not to touch the machine (if it has an on button, push it with your knuckle)

Watch a microbiologist in a washroom. When I go in there, I do all the above and then open the door with the crook of my little finger. It’s not foolproof, but a lot better than not washing. If you are still paranoid, buy a small spray bottle of hand sanitizer and carry it in your bag for use after you have left the washroom and before you eat.

I hope you read this far, Paul.

Can legislation control Salmonella?

2009-05-20T14:42:00.000-07:00

Obviously, some very intelligent people think so. Unfortunately many of them misunderstand the control of food safety.

Food safety legislation is similar to the laws governing road traffic. There are lots of requirements for the design and maintenance of vehicles and prescribed behaviours for their operation. Maximum speeds for each piece of road are set by traffic authorities and advised by signs on the roads. If you exceed the speed limit, you might get away with it most of the time, but speed cameras may catch you. Then you get a ticket and a fine. That’s just money and perhaps demerit points on your licence. Do the speed signs and threat of punishment make us better or more responsible drivers?

Suppose we have an accident and injure or kill another motorist or pedestrian. If we are shown to be at fault, perhaps because of ignoring the speed limit, does the fact that we receive a stiff fine make it any better for the injured party or their family? No way.

The recent outbreak of salmonellosis in the US, carried in peanuts, was almost certainly the result of the flouting of many food safety regulations – the factory was dirty and infested and in-process peanuts were not protected from recontamination. Yet the factory had been inspected and the overall level of food safety was pronounced “superior”. It must be pointed out that the inspector was given only one day to inspect a factory processing several million pounds of peanuts each month and was not an expert in this type of operation. A federal investigation team later discovered that company testing records showed that Salmonella had been found in its products on at least 12 occasions since June 2007. Those products were apparently retested until negative results were obtained and then released to the market.

At least nine people have died from salmonellosis associated with the peanut products and 22,500 were sickened. The existing legislation clearly did not protect them. Some products containing the affected peanuts are apparently still on retail outlet shelves.

In a radio and television address to the American people on 14th March*, President Obama offered his “top ten” ideas for improving food safety. He noted that only about 5% of the 150,000 food production premises were inspected last year, so one billion dollars would be invested in the FDA to increase its ability to inspect premises. Penalties for selling unsafe food would be increased. Unfortunately, he then went on to state that only government can ensure that foods are safe to eat. Wrong, Mr. President!

Food safety is a partnership of trust between government, food producers and suppliers and the consumer. Sure, regulations are required and must be enforced, but no inspection force can guarantee the production and supply of safe food; the manufacturers must be committed to doing so on every day of the year, whether the inspector is due or not.

* http://www.youtube.com/watch?v=lkKp02lluq8

Black-balled peas

2009-04-14T17:15:00.000-07:00

If Talleys of New Zealand have been correctly reported, it seems to me that they have placed the wrong priority on their response to the complaint by Humphrey Elton about his finding Black Nightshade berries in a pack of frozen peas last August. A number of other contaminated packs of peas and beans have turned up since then, the latest being frozen peas and corn last week. One complainant has claimed that almost half of the peas were actually Black Nightshade. If that really is the case, then there is a serious problem in the factory or on the farms.

According to Mr. Elton, Talleys informed him that this is a common agricultural weed and nothing to worry about. He received a cheque for five dollars as compensation.

The New Zealand Food Safety Authority has noted that the berries are “mildly toxic and should be avoided; the contamination is a food quality issue”. It seems that it has been an issue for at least 8 months, but for some reason has only recently hit the headlines.

The fact is, Mr Elton and other consumers bought frozen vegetables. They did not expect to receive anything else in the pack. Being told that the berries are nothing to worry about is akin to complaining to the waiter about a fly in the soup and then being told not to let other diners hear - it’s extra protein and a bonus.

In a world where consumers are highly aware of food safety and quality, I would have expected a more pro-active response from the company. They could have told the complainants that they were very sorry about the contamination and that they were investigating the occurrence and should not have offered such a miserly compensation. If the problem has been known since last year, they should have been doing something about it long ago. What a difference this would have made to the public perception of the company. The downside is that Paul Henry (TVone Breakfast host) would have been robbed of an opportunity to clown around, testing frozen peas by hitting them with a mallet on the Breakfast table.

How could the contamination have occurred? The most likely causes are excessive growth of Black Nightshade in the fields as a result of favourable weather conditions and failure to control this growth by suitable spraying. When the peas are harvested, a harvesting machine cuts the whole pea vine and separates the peas from the other parts of the plant. The harvester cannot differentiate peas from nightshade berries. Sorting and separation in the processing plant was obviously ineffective.

The temperature's rising (but why?)

2009-03-28T01:00:00.000-07:00

I was recently asked to explain some of my comments on detection of faecal coliforms. <See Coliforms and Faecal Contamination Wednesday, July 18, 2007>

I have extracted the essentials of the questions below:

“Since the coliforms when tested… are grown at optimum growth temperature of 37C, why would you need to raise the faecal coliform test temperature to 44.5C to show thermotolerant E. coli are present? Why would food safety people be looking for thermotolerant bacteria in food rather than bacteria that grow at normal temperatures?”

In my article, I provided some background information on "faecal indicator microorganisms", which we use to show that a food or water sample may have been contaminated with faeces. These tests originated in the early days of public health services and safety of public water supply. The coliforms are easier to detect and enumerate than are Salmonella or Shigella or faecal viruses. (Salmonella and Shigella are not coliforms). The reason for incubating at 44.5C to demonstrate the presence of Escherichia coli dates from 1904 when Eijkman suggested it as a means of separating the "B. coli" originating in the faeces of warm blooded animals from the strains characteristic of cold blooded animals and thus providing us with a means to detect faecal contamination of water supplies by warm blooded animals, including humans.

So the answer to the first question is “we are not particularly interested in thermotolerant coliforms; rather we want to show that the water supply may have been contaminated by human wastes and hence potentially contains faecal pathogens”.

Having said that, of course there are other areas of food microbiology where we are very interested in the presence of thermotolerant or thermophilic bacteria. If we pasteurize milk with plate heat exchangers (the standard method) we may find that the cooling stages become colonized by thermotolerant streptococci, which may cause spoilage. In the case of canned foods, we find that some sporeforming bacteria can survive even a very rigorous thermal process. These bacteria are of no public health significance, but they may cause spoilage if the cans are held at high temperatures (greater than about 40C) as might be found in storage facilities in very hot countries or in a restaurant kitchen.

Tha’s gorra eat a peck o’ muck afore tha dies.

2009-03-14T13:46:00.000-07:00

For those readers not lucky enough to have been born in Yorkshire, northern England, an approximate translation of this old expression is “You will eat a barrel-full of dirt during your lifetime”.

What brought that on? According to Abby Alford, writing in the Western Mail (1), there may have been some scientific basis to the saying. Bangor University lecturer, Dr Prysor Williams, believes that an obsession with cleanliness reduces contact with dirt and thus with harmful bacteria. Our immune systems become weakened, leaving us susceptible to infection. Unfortunately, the evidence for this view is somewhat lacking, though Dr. Williams is not the only one to have argued this.

Stuart Levy, Director of the Center of Adaptation Genetics and Drug Resistance at Tufts University, provided substantial evidence that the substitution of anti-bacterial agents for good old soap and water increases the ability of bacteria to develop resistance. A few bacterial cells containing genes that confer resistance to the antibiotics can protect neighbouring sensitive cells, rendering the antibacterial agent ineffective. Levy’s group tested the ability of Escherichia coli to mutate to become resistant to triclosan, which inhibits an enzyme involved in fatty acid biosynthesis and thus interferes with membrane biosynthesis. The work was published in the prestigious journal Nature.

In a carefully constructed randomized, double-blind trial, Elaine Larson and her co-workers have also shown that using antibacterial home cleaning and hand-washing products has no significant effect on the incidence of infectious disease symptoms (2).

The take-home message is that while cleanliness may be next to godliness, we do not live in a sterile environment. If we try too hard to protect ourselves and our children from microorganisms, we don’t give our immune systems the chance to develop resistance to bacterial pathogens.

(1) http://www.walesonline.co.uk/news/wales-news/2009/02/16/
how-obsession-with-cleanliness-could-be-making-us-ill-91466-22935582/

(2) Annals of Internal Medicine, 2 March 2004, Volume 140 • Number 5 321

Peanut butter with that little bit extra

2009-01-19T12:46:00.000-08:00

Over the last couple of weeks, Peanut Corp. of America has recalled 21 lots of peanut butter manufactured in its Blakely plant in Georgia. The product has been linked (by molecular biology techniques) with clusters of Salmonella infections in schools, long-term care facilities, hospitals and other institutions. Genetically indistinguishable strains have been isolated from the product and from patients. 470 people in 43 states have been confirmed as being infected with genetically indistinguishable strains of Salmonella Typhimurium and 90 have been hospitalized. Unfortunately, at least six deaths have been attributed to this outbreak.

The FDA has taken the extraordinary step of urging consumers to postpone eating any commercially prepared or manufactured products containing peanut butter and institutionally served peanut butter (because the implicated peanut butter is supplied only in bulk) until further information becomes available as to which products may be affected. Clearly, this will have far-reaching effects and we are already seeing voluntary recalls of various products in Tennessee, Indiana and New York.

How could this situation have arisen? This is not the first time that peanut butter has been linked with Salmonella infection. The New Zealand Food Safety Authority classes peanut butter as a prescribed (high risk) food because it is produced from peanuts, which have been found to contain mycotoxins (including aflatoxin), mould and insects. So the potential hazards are known. We need to go back and look at the process of peanut butter manufacture for a possible explanation of the current outbreak. The following description is something of a simplification:

Peanuts are actually groundnuts – the flower wilts and bends over, penetrating the ground. The peanut forms under the ground. Harvesting, cleaning and pre-preparation is an involved process, but the most important process is drying to a moisture content that prevents mould growth. The peanuts are shelled, roasted at around 175C and then cooled quickly to 30C. Any Salmonella present on the peanuts is by now destroyed. The peanuts are finely ground and sweetener, salt, oil if necessary and emulsifier are mixed in. The mix is hot filled at around 38C. A further pasteurization step in the jars in a hot water shower may be used here, but not always.

Now we can see where the problem may have arisen. Roasting and blanching are the only lethal process steps in the manufacture of peanut butter. Any contaminating microorganisms entering after these steps may survive in the finished product. Where could Salmonella come from? We don’t know about the Blakely plant yet, but birds often carry Salmonella, so strict control of birds and insects is required. Discharge of fines onto the roof of the factory may attract birds, which defecate on the roof. If the building is not well maintained, rain can wash the contaminating bacteria into the plant. A leaky roof and sprinkler system was the cause of an outbreak in February 2007 at the ConAgra Foods Inc. plant in Sylvester, Georgia. In that case, the Salmonella were thought to have come from raw peanuts or peanut dust. Equipment may harbour Salmonella in seals and hard-to-clean parts. Personnel may also carry Salmonella into the plant, either in their intestines or on footwear, so again, careful supervision of employee hygiene practices and use of red line areas in the post blanching operations is the way to control contamination.

It will be interesting to see what the FDA comes up with in the current investigation. When it’s all finished, this blog will carry a further article.

Is Food less safe these days? Part 3

2009-01-01T00:43:00.000-08:00

The final in this three part New Year soliloquy on food safety

You'll find the earlier parts in the panels below this one.

Communication: Globalisation has had another effect: within hours we know what has happened in other parts of the world. Multimedia cell phones allow people to send pictures and text; the Internet lets ordinary people put their thoughts in front of anyone who has a computer and of course the news media have worldwide coverage and transmit reports via satellite to every continent. The effect of all this is that we know almost immediately of large scale or unusual cases of food poisoning and food fraud as they occur throughout the world, thus increasing the perceived frequency of incidents.

Evolution: When I was an undergraduate microbiologist in the '60s, E. coli O157:H7 was unheard of. It was first identified as a human pathogen in 1982. Other new serotypes have also been recognized, usually as a result of an outbreak. It appears that evolution is continuing at a visible rate, at least in the microbial world. Dr Chris Bell and Alec Kyriakides† have expressed it beautifully: “Genetic promiscuity is facilitated by a range of genetic elements including plasmids, transposons, conjugative transposons and bacteriophages* . The ability to evolve through horizontal gene transfer and acquire ‘foreign’ DNA, has resulted in novel phenotypes and genotypes emerging”. This mix-and-match behaviour has resulted in the formation of diarrhoea-causing strains that possess previously unreported combinations of virulence factors. The study of DNA sequences in old lineages of E. coli has shown that these lines have acquired the same virulence factors in parallel. Natural selection has thus favoured an ordered acquisition of genes and a progressive build-up of molecular mechanisms that increase virulence (Reid et al., 2000. Nature, 406 64-7). Just this week in the journal Science, John Chen and Richard P Novick have reported that staphylococcal bacteriophage can transfer staphylococcal pathogenicity "islands", pieces of DNA containing superantigen genes and other transferable elements, to Listeria monocytogenes at the same high frequencies as they transfer within Staphylococcus aureus. See here

This might sound esoteric, but the practical result is that we will see more novel virulent bacteria that will in the future cause new food borne illnesses.

Obviously, the examples I have given above contain elements of more than one of the highlighted causes. Does this all add up to an answer to my original question? I think that we can draw some general conclusions.

• Modern food manufacturing processes may be technically more advanced than traditional food production
• These processes can be very reliable and make vast amounts of safe food at affordable prices
• When something does go wrong, the results may be catastrophic because of the scale of operations
• Human error and fraud are ever-present hazards to a safe food supply
• Our perception of the frequency of food poisoning or food fraud incidents may be influenced by the ease of international communication
• Microbial evolution means that we will never produce totally safe food

On balance, I think that our food is actually safer than it was 25 years ago.

†Bell, C. & Kyriakides, A. (2002) Pathogenic Escherichia coli. IN
Foodborne pathogens: Hazards, risk analysis and control. Blackburn, C. de W. & McClure, P.J. Woodhead Publishing, Cambridge, UK.

* Plasmid – a small circular independently replicating piece of DNA in bacteria; Plasmids often carry virulence factors, antibiotic resistance or toxin coding genes
Transposon - sequence of DNA that can move around to different positions within the genome of a single cell, possibly causing mutation
Conjugative transposon - integrated DNA elements that excise themselves to form a circular intermediate, which can transfer by conjugation to a recipient and integrate into the recipient's genome. Conjugative transposons have a broad host range and are probably as important as plasmids in the spread of antibiotic resistance genes in some genera of disease-causing bacteria (A A Salyers et al., (1995) Microbiol Rev. 59(4): 579–590).
Bacteriophage – a virus that infects bacteria and may ferry small sequences of bacterial DNA from one host cell to another. The DNA may integrate into the recipient’s genome and confer new characteristics, such as the ability to synthesise new enzymes.

Is Food less safe these days? Part 2

2009-01-01T00:32:00.000-08:00

You'll find Part 1 in the panel below this.

Globalization: The globalized food supply means that raw materials may be processed outside of our own country and the foods transported to our local suppliers for distribution. The opportunities for poor process control and contamination are again significant. Many countries rely heavily on imports of food. The development of Chinese industry means that these imports are often sourced from China, though not exclusively. The Chinese government is moving to improve control over food manufacture, but faces an uphill battle in such a large country with so many diverse regulatory authorities.

Greed: The huge demand for food is a temptation for some unscrupulous manufacturers to try to make a fast buck by adulterating food or passing off poor quality materials. The prime example in our time is the use of melamine to increase the apparent protein content of milk and pet food. See here However, food fraud has been going on literally for centuries.

Adulteration of food is usually done with inferior materials to increase the bulk of the real item and thus increase profits. In 1820, a German scientist Frederick Accum published his book “A Treatise on Adulterations of Food and Culinary Poisons”. He described sloe leaves added to tea, lozenges made from pipe clay, custards poisoned with laurel leaves, floor sweepings mixed into pepper and copper used to colour pickles green.

In 1857 Arthur Hill Hassal, an English physician and microscopist, wrote a book “Adulterations Detected, or Plain Instructions for the Discovery of Frauds in Food and Medicine”. He noted that “Adulteration prevails in nearly all articles which it is worth while to adulterate, whether it is food, drink or drugs”. Watering of milk or of “cream ice” was a popular activity, but clay and dust were used to bulk up many foods. These days, companies have analytical techniques to detect adulteration of food, but this works only if the company is not involved in the fraud. Government organizations like the New Zealand Food Safety Authority and the US Food and Drug Administration cannot guarantee the safety of foods by end product testing. See here The best that can be achieved is management of food safety through risk management programmes.

The following new book offers interesting reading: Wilson B (2008). “Swindled: the dark history of food fraud, from poisoned candy to counterfeit coffee”. London: John Murray Publishers.

In the final, Part 3: click here: Communication and Evolution

Is food less safe these days? Part 1

2008-12-31T23:41:00.000-08:00

Over the Christmas period I have done a lot of eating and drinking and being merry. I’ve also done a lot of thinking about food safety. In the last year we seem to have read almost daily of Listeria being found in deli meat, that babies have been poisoned by formula milk, children have been hospitalized with failing kidneys resulting from Escherichia coli O157:H7 infection, that melamine has turned up in yet another food product, or that an established company has closed its doors because of massive losses resulting from a food recall. Is our food less safe these days?

I don’t think that there is a simple answer, but I do have some suggestions. In this three-part posting I’ll share them with you.

I think that the whole thing can be analysed under a few subheadings.

Food Preparation: Some of my Christmas celebrations have involved large functions where caterers have served meals to hundreds of partygoers. These meals could not have been produced on the premises, so the food must have been pre-prepared and transported to the venue in insulated containers or perhaps reheated before serving. Other celebrations have been more modest, catered by the “bring a plate” approach. We have had barbecues, where foods were cooked outside on gas or charcoal burners. All of these scenarios have at least one thing in common – the foods were prepared by others for us, perhaps in non-ideal conditions, or were not eaten immediately after preparation. The opportunities for contamination of the food, incomplete cooking and growth of bacteria were numerous.

Centralization: The economies of scale lead to evolution of very large manufacturing operations with huge distribution networks. Smaller companies are squeezed out of the market. If something goes wrong in this supply chain, the impact can be widespread. In 2000, Staphylococcus aureus bacteria built up in raw milk that was unable to be cooled for several hours after fat separation in Snow Brand's Taiki factory. Ultimately, at least 14,700 people, mostly in western Japan, were affected by food poisoning after consuming milk or related products made by the company. Topps Meat Company, a US company specializing in manufacture of frozen ground beef, recalled 21.7 million pounds of ground beef, bringing the total recalls in the US between April and October 2007 to over 30 million pounds of red meat, mostly hamburger. The reason was that there had been a number of cases of Escherichia coli O157:H7 infection tied to its products. There was evidence of an inability to identify unique batches of product and this probably contributed to the size of the recall. The USDA also cited the company for “inadequate process controls in the non-ground meat production line”.

Ignorance may play a part. Last Easter in New Zealand, 22 people were poisoned, some seriously, when they consumed comb honey which had been made by bees that collected honeydew from tutu plants (Coriaria arborea) infested by vine hoppers. The upshot was that the honey contained large amounts of the toxin tutin, which is found in the sap of the tutu plant. In April last year, I wrote that this was not a new problem. See here Indeed, F.S. Fastier, Roslyn Emeritus Professor of Pharmacology at University of Otago, wrote last week that he was present at a meeting of interested parties in Wellington in 1964, where the issue was debated. Beekeepers have known how to manage this hazard for a long time, but a small beekeeping operator last year apparently failed to take account of the fact that there were tutu bushes in flower in the bees’ foraging area and continued to sell the comb honey. The resulting poisonings have led to the New Zealand Food Safety Authority introducing legislation to limit the amount of tutin that may be present in honey offered for sale. See here
This has not pleased everyone – some think the regulations don’t go far enough, some in the industry consider them to be unnecessary. However, NZFSA could not stand by and do nothing without risking the health of the population and the future of the lucrative New Zealand honey industry. The regulations will be reviewed at the end of the 2009 season.

In Part 2: click here: Globalization and Greed

Melamine

2008-09-21T14:07:00.000-07:00

Perhaps, like me, you have been wondering why some unscrupulous Chinese suppliers would put plastic first into pet food (2007) and then milk (2008). The extent of my knowledge was that melamine is a monomer used in making hard plastic products as diverse as bowls, shoehorns and bench coverings. It seemed to me that such a compound would be more expensive than the product it was substituting and thus not worth the effort. So I did a little searching on the Internet.

There is some confusion in terminology. Melamine is a ring structured compound containing a lot of nitrogen (66% by mass). It is combined with formaldehyde to produce melamine resin, a thermosetting plastic. However, the plastic is also often called simply “Melamine”. There are a number of ways of making the monomer; these days it is usually made from urea, but it can also be made from coal. China is the largest producer of melamine in the world.

The current story probably has its origins in a patent from 1958, which described the use of melamine as a source of non-protein nitrogen in cattle feed. However, a study conducted in 1978 suggested that melamine is digested more slowly and less completely than cottonseed or urea, so its use is probably limited.

Melamine itself has a low toxicity – approximately the same LD50* as sodium chloride. However, the combination of melamine and cyanuric acid in the diet causes acute renal failure in cats. This came to light after the contaminated pet food incident. I think it is unlikely that many humans consume cyanuric acid in their diets, though this compound has been approved by FDA for use in animal feed and is used as a precursor to N-chlorinated cyanurates, which are used to disinfect water e.g. in spa and swimming pools. Chronic ingestion of melamine can lead to formation of kidney and bladder stones and it may be that this is a particular problem in very young children.

Perhaps the reason for the adulteration of the Chinese products was that melamine can increase the apparent protein content of the food. It has been reported that melamine scrap is widely incorporated into livestock and fish feed in parts of China (New York Times, 30th April, 2007). Since “melamine scrap” is an impure and less valuable form of the chemical produced as a by-product, for example in coal gasification, this could explain why it might be economical to replace milk or meat protein with this non-protein nitrogen source if it can be concealed from the authorities and customers. Measurement of protein content by the Kjeldahl or Dumas methods, which actually measure nitrogen content, would not detect the adulteration. Testing for melamine directly is difficult and expensive, though test kits are now available.

As an aside, since melamine is used in food packaging and tableware, small amounts of the compound (parts per million level) may be found in foods and beverages as a result of migration from melamine polymers in contact with the food. These levels are not considered to be a health risk.

* LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals.

Exercise viewed from the relative safety of the couch

2008-08-23T21:30:00.000-07:00

We are constantly urged to get out and do some exercise. This can be as simple as walking to work or doing a workout in the gym. However, walking at this time of the year in New Zealand has the distinct disadvantage that you can arrive at work looking like a drowned cat. The gym is less of a problem in that respect, but just pumping iron or running on a treadmill can get mighty boring.

What about mountain or cross-country biking? That can get your heart rate up and can be very exciting. There can also be a downside. Campylobacter.

There, I bet you immediately thought “What has mountain biking got to do with chilled chicken?” Certainly, we have heard a lot about Campylobacter and chicken meat over the last couple of years, much of it not good news. But this piece is not about transmission in poultry.

On July 5th and 6th this year, a mountain bike marathon was run on Builth Wells, Wales. The two-day event attracted 947 participants, up to 160 of whom became ill after the event. The conditions were very muddy and the course was contaminated with “sheep slurry”. The result was that contaminated mud splashed over the riders and their gear. An investigation* revealed that accidental ingestion of mud was the most statistically significant risk factor. Consumption of energy drinks and energy bars from feed stations was also associated with infection. It is easy to see how these factors might be linked – riders covered in mud would contaminate their drink bottles and dirty hands could transfer mud to food. Only the competitors became ill – support crew and visitors were not involved.

The running of this type of event over muddy agricultural land makes it almost inevitable that competitors would be exposed to zoonotic infectious agents, such as Campylobacter, Salmonella and Listeria.

It is very tempting to ask whether the high incidence of campylobacteriosis in new Zealand could be at least partly explained by our passion for strenuous outdoor sports that involve getting muddy and the high proportion of the country given over to farming. We already have some data on risk factors in New Zealand see http://foodsafetywithjaybee.blogspot.com/2008/04/what-interests-you-most.html
Perhaps it would be worth including questions in the surveys about contact with mud and activities such as cross country running or rugby.

* Griffiths, S. et al (2008) Preliminary report of the epidemiological investigation into the outbreak of diarrhoeal illness in Mountain Bike Marathon participants, Builth Wells. National Public Health Service for Wales

A hard course to row: the colossal task of making food safe in China

2008-08-22T20:23:00.000-07:00

The heartbreaking spectacle of New Zealand Olympic rower Mahe Drysdale pulling to the front of the field in the finals of the single sculls and then fading only 250 m from the finish will be hard to forget, no matter which country you support. We have all experienced the debilitating effects of food poisoning and some of us know how it feels to go beyond our physical limits, though perhaps at a much lower level of competition.

Drysdale apparently suffered a food borne infection that left him unable to eat and severely dehydrated. These are common sequelae of food poisoning. The normal way of dealing with this is rest and careful intake of suitable rehydration fluids. To go out and exercise strenuously in high temperatures would definitely not be recommended. That he did is a testament to Mahe’s true grit and determination.

It seems that Drysdale was not the only Olympian to suffer from food poisoning. About 15% of the U.S. track team also became ill, despite their team managers having taken precautions to protect them. Large quantities of food were imported into China from the United States to reduce the risk from eating local food. However, the track team spent a period of training in Dalian, 300km from the Olympic Village and did not have access to the imported food. The infections could not be attributed definitively to food, according to a chef brought from the U.S. to prepare the team’s meals. He suggested that water used to prepare the food might have been the source of contamination. The team doctor described the illnesses as “normal stomach bugs… not widespread… not out of the ordinary for international trips”.

Whatever the explanation, to find 15% of a very healthy population succumbing to gastro-intestinal illness in such a short period suggests to me a food or water borne infection or indirect contact with infective faecal matter, perhaps via an unclean restroom surface. (Norovirus is often transmitted in this way, though at this stage there is no indication that the team contracted Norovirus).

It is actually quite difficult to avoid all possible sources of infection. Drinking only beer, wine, hot tea or sealed bottles of water and eating only hot foods helps, but also means that you miss many wonderful culinary experiences. Even fresh fruit may have been washed in contaminated water before being sliced and this has sometimes been shown to be the vector for intestinal pathogens.

China has tried to provide safe food for teams and spectators at the Olympics. Unfortunately, their approach illustrates the enormity of the task and the collateral damage of draconian measures. John Garnaut, writing in the Sydney Morning Herald on 15th August, told of chefs and hoteliers across Beijing being forbidden to purchase foods from their normal suppliers. Fresh and processed foods could be bought only from a Government-approved list of 64 suppliers. This effectively gave those favoured suppliers a licence to print money, so costs have gone up by as much as 1200 per cent. Though it has avoided food scandals so far, there is no guarantee that food is any safer.

In a parallel to the problem of fake luxury goods, it will require a long process of education and rooting out of corrupt food suppliers - those who use substandard materials, illegal chemicals and inadequate processes to make a fast buck - before we can be reasonably sure that food in China will be as safe, microbiologically and chemically, as our food here in New Zealand.

Coming soon to a store in New Zealand?

2008-08-13T20:41:00.000-07:00

I have written several times about the potential hazards of consuming raw milk and raw milk products. Search this site using keyword “raw milk” for other posts.

Currently the New Zealand food regulations allow only three particular hard and very hard Swiss cheeses, extra-hard Parmesan style grating cheeses like Grana Padano, Pamigiano Reggiano, Romano, Asiago and Montasio and the semi-hard Roquefort cheese. Local manufacture of similar products is not permitted. See www.nzfsa.govt.nz/publications/media-releases/2008/2008-08-07-raw-milk.htm

The New Zealand Food Safety Authority is now asking for submissions on a proposed framework for the manufacture, importation and sale of raw milk products. See www.nzfsa.govt.nz?consultation

Aficionados of raw milk cheeses will applaud this move. It is quite possible to produce safe cheeses without pasteurization of milk and, provided that the resulting products are safe, manufacturers and consumers should be given the opportunity to make and taste them. However, the process requires strict control of animal health and rigorous processing hygiene - good regulations and inspection will be needed.

Even the cheesemakers are divided on the desirability of permitting the manufacture of raw milk cheeses. One, quoted in the Otago Daily Times on 11th August 2008 said that cheeses made from non-pasteurised milk could be “lovely", but they could also be “bloody awful stuff". The explanation for this is that pasteurized milk contains only heat resistant bacteria, such as some Streptococcus species and sporeformers. The cheese is made by inoculating the pasteurized milk with known cultures of "starter bacteria", which will produce lactic acid to coagulate the milk protein and produce a curd. When cheese is made from unpasteurized milk, the bacteria present in the raw milk may grow beside the starters. This can result in more complex flavours, but can also lead to variation between batches. Unfortunately, the non-starter bacteria can sometimes cause disease, such as salmonellosis and campylobacteriosis, or may produce toxins, such as staphylococcal enterotoxin.

Softer raw milk cheeses represent a greater risk to the consumer because of their higher water activity, which allows some pathogens to survive and grow. Control over the milk production and handling and the cheesemaking process itself must therefore be absolutely spot-on for these products.

Under the proposed framework, raw milk products would be categorised according to the risks they present. Category one products would pose no greater food safety concerns than pasteurised cheeses, such as Parmesan-style raw milk cheeses. Category two products would pose a low risk for the general population but vulnerable consumers with reduced immunity might be at greater risk. Products in this category would include semi-hard Roquefort. Category three would cover those raw milk products that cannot currently be produced to an acceptable level of safety for the general population. (As far as I know, this category has not yet been defined more closely).

Assuming that the consultation process approves the proposed framework, locally produced raw milk cheeses and other raw milk products may soon hit the delicatessen and specialty store shelves. It may be too soon to expect these products to be sold in supermarkets.

Would I eat raw milk cheese? Probably not until the framework were shown to be working well and the suppliers had built up a record of selling safe products. Even then, I would eat only the hard or semi-hard varieties. Would I give it to my little granddaughter? Not a chance! Raw milk products are not for little children or the immunocompromised.

Tuberculosis and Mexican cheese

2008-06-08T21:00:00.000-07:00

Quite by chance, on the day I was writing my last blog article on raw milk, the Orange County Register published an article by Doug Irving on an outbreak of tuberculosis in San Diego. See http://www.ocregister.com/ocregister/homepage/abox/
article_2060722.php?orderby=TimeStampDescending&showRecommended
Only=0&oncommentsPage=2#slComments

Mycobacterium bovis is relatively rare in humans, but can be serious and difficult to treat. It is thought that the disease jumped from cattle to humans somewhere between 8000 and 4000BC, when cattle were domesticated. There is archaeological evidence that humans suffered the disease, pulmonary tuberculosis, which may have been contracted through consumption of raw milk. The human specialized form M. tuberculosis was probably spread by migrating Indo-Europeans and by 1000BC it had spread to the whole of the known world.

It appears that in the San Diego area, the disease is spreading primarily through the Latino population and scientists there believe that it may be being brought into the country from Mexico in queso fresco, a popular soft crumbly cheese that may be produced as a cottage industry.

The article in the OC Register contains some inaccuracies. Not all milk sold in the USA must be pasteurized; it depends on the particular State legislation. In addition, the article implies that the outbreak has suddenly flared. However, the actual study by UCSD Medical Center and county health officials, showed that between 1994 and 2005, there were 3,291 cases of active infection reported by the county's Tuberculosis Control Program and of those, about 8 percent were ill with M. bovis. Roughly the same pattern was observed in 2007.

The sale of raw milk cheeses in New Zealand is currently limited and subject to strict controls. See http://foodsafetywithjaybee.blogspot.com/2007/06/
free-choice-or-safety-of-population.html
Extra hard Italian Parmesan-style raw milk cheeses like Grana Padano, Pamigiano Reggiano, Romano, Asiago and Montasio have a low water activity of about 0.693, which prevents the growth of bacterial pathogens.

It had to happen!

2008-06-05T14:46:00.000-07:00

In the USA, the argument about raw milk still rages. We now see the spectacle of lawyers claiming that consumers are being deprived of their rights to choose their food, while others sue the suppliers for selling dangerous milk.

The raw milk lobby claims that pasteurization robs the milk of its nutritional value and the natural enzymes that help the human digestive system. I am not aware of any scientific evidence to support this. They also vociferously claim that pasteurization kills the “good bacteria”. The zealous consumers claim that their rights are being trampled if they are prevented from buying the product. The regulators point to the dangers of consuming raw milk, such as the diseases caused by Salmonella, Campylobacter, Escherichia coli, Listeria and others, a point conveniently ignored by the raw milk proponents.

The hazards of consuming raw milk have been known for a long time. In Ontario around 1900, over 10% of all childhood tuberculosis was thought to be caused by unpasteurized milk. The rate of tuberculosis infection and many other milk-borne diseases in children fell dramatically after enactment of a law in 1938 requiring milk to be pasteurized; this was hailed as a major achievement.

The fact is that between 1998 and 2005, a total of 45 outbreaks resulting in more than 1,000 illnesses, 104 hospitalizations and two deaths due to raw milk or soft raw milk cheese were reported to the Centres for Disease Control and Prevention. There have been more recent, high-profile cases. Pathogens were found in 13 percent of bulk tank raw milk samples by a survey of Pennsylvania dairy farms in 2006. In California, 2008, new regulations set a limit of 10 coliforms per millilitre of raw milk. Raw milk suppliers maintain that the regulation will put them out of business, which suggests to me that they feel unable to meet this specification. But it's the same standard used for pasteurized milk. <For an explanation of the use of coliforms, see "Is hamburger a greater risk for E. coli" this blog, posted 3rd May 2008>.

Farmers who are selling raw milk are able to charge a significant premium for their product and understandably wish to continue supply. However, nothing comes without a price, and the right to sell a particular food product imposes certain responsibilities. Some American consumers have contracted serious disease from drinking raw milk. Unfortunately, children have no choice in the source of their milk and several have suffered haemolytic uremic syndrome (which has a 90% mortality rate without treament) and a number have required kidney transplants. The suppliers are now being sued.

In New Zealand, NZFSA has recently renewed its warning to consumers about raw milk cheeses, which have recently been approved for sale here. People with compromised immune systems, the elderly or pregnant women are urged to avoid these products.

It’s happened before, it’s happened again and it won’t be the last.

2008-05-06T21:44:00.000-07:00

The Queenstown District Court (South Island, New Zealand) was told an all too familiar tale a couple of days ago. Two women had been poisoned and subsequently hospitalized after consuming a contaminated drink. On this occasion, the drink was mulled wine; the contaminant was sodium hydroxide – industrial dishwashing liquid.

At first sight, this would seem to be an impossible occurrence. Closer inspection shows a familiar pattern. I expected that the mulled wine would have been made on the premises from wine, sugar, cinnamon stick etc. However, the drink was apparently dispensed from a bulk container of pre-prepared “mulled wine”. Unfortunately, the container appears to have been used to deliver the cleaning chemical. Presumably, the label was not changed and the person serving the product didn’t detect the substituted liquid. It is not clear to me why the industrial chemical looked to all involved like mulled wine.

This is utterly poor practice of the worst sort. I have been teaching HACCP for the last 30 years and during the whole of that time, the use of food containers for other materials has been proscribed as part of the food safety plan. Proper labelling of containers is also critical. There have been so many cases where this practice has resulted in injury or even death that I have lost count. Some examples include preservative being mistaken for sugar; fire retardant powder being mistaken for cattle feed; cleaning agents being used in food preparation instead of the expected food ingredient. In one admittedly non-commercial case, a person died after drinking from a spirit bottle containing paraquat - a herbicide.

No food container should ever be used to store non-food chemicals; chemicals should not be stored with food ingredients and all containers should be clearly labelled with the identity of the contents.

Is hamburger a greater risk for E. coli?

2008-05-03T18:44:00.000-07:00

The subject of coliforms in food and specifically the question about hamburger comes up often in the referrals to this blog.

Coliforms are used in the food industry as indicators of general hygiene. This sounds simple, but it is not quite straightforward; we need to understand what coliforms are and how they are measured before we can draw conclusions.

The term “coliform” does not refer to a unique species. In fact, coliforms are a group of bacteria defined by the test used to detect them. Thus, we can carry out a simple culture test that will count or show the presence or absence of this group. Each country uses slightly different tests. One protocol defines coliforms as:

“Gram negative rods that produce acid and gas from lactose in the presence of bile salts at 37 C in 24 to 48 hours”

Notice that there is no mention of genus or species or connection with faecal contamination. In fact, the group includes several genera that are capable of growing in the environment and have no faecal connotation, so finding coliforms on lettuces should not be cause for undue concern. What we can say is that all of these bacteria should be killed by pasteurization temperatures, so if they are found in pasteurized foods, the hygiene of the process has been poor.

If we want to show that faecal contamination of food has occurred, we do a test for Escherichia coli, which is found at high concentration in faeces. This test for “faecal coliforms” was originally used to test water, where the organism cannot grow. The situation in food is a little more complicated because the organisms may grow in the food, but the finding of E. coli in food is good evidence of faecal contamination. Properly pasteurized food should not contain any faecal coliforms. Raw foods, such as leafy vegetables, can become contaminated by faecal coliforms if birds or animals have access to the crops. This was the probable cause of E. coli O157:H7 contamination of raw spinach last year.

Meat animals all have E. coli in their intestines and there is a possibility of contamination of the carcase by spillage of gut contents during slaughtering. This contamination will initially be on the meat surface, but will be distributed throughout the meat if it is minced or ground. This is why steak can be eaten “rare”, since the interior of meat from healthy animals is sterile – all that is required is for the exterior to be cooked to a temperature of about 70 – 75 C. However, hamburger patties are made from ground meat and must therefore be cooked right through to ensure destruction of faecal bacteria that may have been mixed in. Americans tend to eat hamburger cooked less thoroughly than in other countries. The USDA suggests 71.1 C (160 F) for beef burgers. So the real issue is not that hamburgers are at greater risk of contamination, but that undercooking them may allow E. coli to survive.
See Guaranteed safe At what cost (?) October 17, 2007
http://foodsafetywithjaybee.blogspot.com/2007/10/
guaranteed-safe-at-what-cost.html

What interests you most?

2008-04-21T21:09:00.000-07:00

My Sitemeter collects statistics on usage of this blog (don’t worry, you can’t be identified) including pages visited and referrals from search engines like Google and Yahoo.

I looked through some recent stats and found that the most common questions referred to the safety of chicken (by far the most frequent referral), unpasteurized milk, coliforms and how bacteria can get into food. There were one or two surprising enquiries, but I won’t go into those.

Over the next few posts I’ll visit some of the more popular questions, starting with a report from New Zealand on campylobacteriosis and poultry.

The March 2008 Monthly Surveillance Report from ESR makes for interesting reading. http://www.surv.esr.cri.nz/surveillance/monthly_surveillance.php?
we_objectID=1548

The incidence of campylobacteriosis in the human population of New Zealand has fallen again. 450 campylobacteriosis cases were notified in March 2008 compared with 1145 cases notified in the same month of the previous year. The current 12 month rate* is 234 cases per 100,000 head of population, compared with 386 for the previous 12 months to March 2007 – a 39% reduction. Compared with the rates of other infectious diseases surveyed, this is a very significant achievement.

Though there is currently no direct evidence, at least some of this reduction must be because of the strenuous efforts made by the poultry industry to reduce the levels of contamination on fresh poultry and poultry products.

The Campylobacter surveillance data contain other interesting observations on the possible source of infection: of the cases where the information was recorded, 51% had eaten food from a food premise (I assume that means a restaurant or take-away); 38% had contact with farm animals; 22% had contact with other people showing symptoms of campylobacteriosis. Other possible links included pre-schools and childcare, drinking non-habitual or untreated water supply or contact with recreational water. A surprising 17% reported faecal contact, while a small proportion reported contact with a sick animal.

Obviously, this information is confounded and incomplete and doesn’t explain exactly how the patients contracted campylobacteriosis. However, it does point to the special nature of life in New Zealand and suggests that we need to look widely to find ways to control our high incidence of campylobacteriosis.

(For further information on Campylobacter, either select "search blog" using the keyword Campylobacter, or go to "So what is this Campylobacter thing?" posted Tuesday 21st November 2006 by clicking the Archive).

How do you know chicken is safe to eat? If you cook it yourself, use a meat thermometer to check the internal temperature reaches 74 C (165 F). The USDA suggests 160 F (71.1 C) for beef burgers. If you buy chicken ready-cooked for reheating, use the same temperatures. If you are going to eat pre-cooked chicken without further heating, make sure you trust the supplier.

* The 12 month rate is based on the cumulative total for the current year (12 months up to and including March 2008), expressed as cases per 100,000

The news just keeps on getting worse!

2008-03-28T19:06:00.000-07:00

After so many years of living with a food microbiologist, my wife has become a valuable food retail spy. Today she told me two more horror stories:

In our local supermarket there is a display stand for unwrapped bakery goods that extends from about chest height down to the floor. The store manager has supplied tongs for customers to use and there are signs asking customers to use the tongs.

Today she arrived at the bakery counter in time to see a mother wrestling the tongs from her toddler. If this were not bad enough, the mother then said to the toddler “I thought you said you were going to eat that”. Grabbing a bun from the child’s other hand, she stuck it back in the cabinet. Now both of them had handled the bun.

Now, I realise that bread buns are not a particularly good growth medium for food poisoning bacteria, but this is unacceptable. Some food borne pathogens have a very low infecting dose. The display cabinet should be arranged so that products and tongs are inaccessible to toddlers. Owners of self-service food displays need to be aware that simply providing tongs does not guarantee the safety of the food they sell. Needless to say, we will not purchase unwrapped goods from that store again.

The second incident was observed on TVNZ’s Good Morning show. Unfortunately, I didn’t see it and have not been able to locate a replay on their website. It appears that The Mad Butcher was on the show and demonstrating the preparation of chicken. After handling the raw chicken, he put his fingers into some spices and tasted a pinch. The bowl of spices was thus contaminated with whatever bacteria were on the raw chicken. A short while later, he put a cooked chicken onto the same chopping board, contaminating it with raw poultry juices.

OK – the Mad Butcher is not a professional chef and neither is Steve Grey, the host for that segment. The poultry industry in New Zealand has had a bad press recently over Campylobacter food poisoning, allegedly transmitted largely via chicken (though in fact we have seen a significant and sustained reduction over the last year in the incidence of the disease in the human population). This sort of example on daytime television, which is probably watched by many young mothers, is perhaps one of the reasons that we see such a high incidence of campylobacteriosis in New Zealand. Young adults are not getting the food safety message and we need to have good kitchen habits shown on our national television channels. We can’t rely on the food suppliers to take total responsibility for control of food poisoning.

This type of poor kitchen practice is not confined to New Zealand; Doug Powell at Kansas State University, who runs the Food Safety Net and writes the Barfblog has castigated some TV chefs in the USA for similar indiscretions (see for example: http://barfblog.foodsafety.ksu.edu/tags/tv/).

Pigeon pie, anyone?

2008-03-28T18:58:00.000-07:00

What does it take to make us clean up our act?

2008-03-10T13:15:00.000-07:00

Having lived in Hong Kong for a while, I am perhaps more aware of the potential for the spread of diseases than the average Kiwi. The Chinese have suffered SARS and bird flu and are very keen to avoid more outbreaks of either. If you sneeze in public, people will stare accusingly at you; people who have a cold will voluntarily wear a face mask out of consideration for others; there are hand sanitizing stations around public buildings and patrons are warned not to feed birds in outdoor eating areas.

With these thoughts in mind, I have been surprised to see the couldn’t care less attitude of some businesses here at home. When a fly crawling over the goods in a bakery was pointed out to the assistant, she shrugged her shoulders and said that it was impossible to keep them out. There is a coffee and cake shop on the podium level of the apartment block where I live. They have a resident population of flies there too. But in addition, they have birds. Not in cages as decoration, but possibly as employees. These birds hop around on the floor and pick up crumbs. They also hop onto the tables on the terrace and finish off the meals left by the patrons – the plates stay on the tables long after the diners have left. This is just not acceptable in any food service premises.

New Zealand has been lucky and so far avoided bird flu scares. However, bird flu is not the only concern. When birds hop around on floors or tables and perch on chairs, they are inclined to leave droppings behind. If eventually an assistant comes to remove the plates, the table will be wiped with a cloth, spreading a thin film of droppings around and probably contaminating the whole surface with faecal bacteria and viruses. Of course, we don’t eat off the table, but it would be hard not to touch it and so there is a risk of ingesting these organisms, particularly if we eat cakes or breads with our fingers.

I would have expected these failings to be brought to the attention of the shop owners by the authorities. Perhaps we also put too much faith in antibacterial sprays. Are they an extension of the plastic glove = bullet-proof syndrome? We need to see safety in practice, not just in a manual on the manager’s shelf. I hope it will not take a SARS epidemic or outbreak of bird flu to convince these businesses to clean up their act.

Campylobacter jejuni - SEM image

2008-02-10T20:23:00.001-08:00

Scanning electron microscope image of Campylobacter jejuni, illustrating its corkscrew appearance and bipolar flagella. Source: Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia.

That Campylobacter problem – it just doesn’t go away

2008-02-09T15:19:00.000-08:00

It has been fascinating to watch the news reports, both here in New Zealand and overseas, over the last few weeks and see the different takes. The New Zealand Food Safety Authority announced on 15th January the introduction of a Code of Practice for the poultry industry. The code is intended to reduce the incidence of campylobacteriosis in New Zealand, which is the highest in the developed world. The code has received mixed reviews and the language used has at times been intemperate. The blame for much of this disease has been laid at the door of the poultry industry as suppliers of “New Zealand’s cheap and dirty food”. In a Radio NZ interview, Dr. Mike Baker claimed that when chicken is prepared in a kitchen, every surface in the kitchen will be covered with bacteria and the aprons of workers in restaurant kitchens will potentially be covered in a layer of Campylobacter.

When interviewed by the Taranaki Daily News, a Tegel spokesman said that the Company fully supported the new code. Sharon Wagener of NZFSA says that the code formalises a lot of what was already happening voluntarily in the industry. However, on the Green Party website their spokesman Sue Kedgley claimed that the code “fails to include some very simple measures to stem the tide of Campylobacter contamination of chicken meat being sold to New Zealanders”. Some of the points raised by Ms. Kedgley in relation to problems of mechanical handling and leaky packaging are not in dispute, but are already being addressed by the industry.

The Taranaki Medical Officer of Health, Richard Hoskins, noted that the Health Board has had interactions with Tegel (which of course is not the only chicken processor in the country) in efforts to reduce the incidence of the disease. He apparently expressed the view that the Board was "pretty impressed with the efforts they are going to".

Michael Brooks, the Executive Director of the Poultry Industry Association of New Zealand, has also stated that based on figures collected by ESR, human campylobacteriosis case rates have been steadily declining since August 2006, in some months showing a drop of 30-35% over the corresponding previous year. Of course, this does not satisfy everyone; the incidence of campylobacteriosis tends to be somewhat variable from month to month and it will require proper statistical analysis over some years to demonstrate a true decrease.

The adversarial approach being taken by some of the interested parties is not, in my view, the best way forward. Nobody has the complete right answer; where has the still small voice of reason and collaboration gone? Wouldn’t it be better if the parties worked together, using scientifically demonstrable facts and not overheated opinion to put together the jigsaw puzzle and solve the problem?

The fact is that human infection by Campylobacter is a very complex problem and simply pointing the finger at the poultry industry will not solve it, no matter what codes of practice are imposed. Take just one point: sub-typing of Campylobacter, using molecular methods, can show the relatedness of various isolates from poultry and from humans. In some parts of the country, a single sub-type is found in up to 20% of human cases and in poultry. In other parts, the sub-typing shows that human cases do not share the same types as found in poultry. Nobody is claiming that poultry does not contribute significantly to campylobacteriosis in New Zealand, but the industry takes this seriously and is doing something about it, having issued its own Broiler Growing Biosecurity Manual in consultation with NZFSA in August 2007. This describes the minimum standards to be used in NZ broiler production systems, aiming at ensuring the products meet food safety and suitability requirements and consumer needs. Campylobacter is a commensal bacterium – it is found in poultry and some other animals and does not cause them to be ill, so getting rid of it is going to require considerable effort and some cost on the part of farmers and processors.

The code comes into force on the first of March 2008.

For more information on Campylobacter, click here

Dangerous probiotics? Probably not

2008-02-03T14:55:00.000-08:00

Readers may have been concerned to hear last week of 24 unexplained deaths among patients with acute pancreatitis, who were being administered probiotics in a study conducted at the University Medical Centre in Utrecht. The deaths occurred between 2004 and 2007 and represented 16% of the 296 patients in the trial. Unfortunately, the original reports are in Dutch and it is difficult to glean the full facts, including the percentage of patients in the control group who died.

It appears that the patients all had serious acute pancreatitis – inflammation of the pancreas. This disease may have a number of causes, but alcohol abuse and gallstones account for 80-90% of cases. Scarring of the pancreas during an attack may lead to chronic disease that can become life threatening.

The research concerned the functioning of probiotic bacteria administered to reduce the effects of the pancreatitis. The investigation was conducted in fifteen hospitals under the guidance of UMC Utrecht. If I have interpreted the press reports correctly, an investigation of the deceased showed that no infection resulted from the administration of the probiotics. However, three factors appear to be involved: treatment with probiotics of patients having organ failure; treatment of patients in intensive care; treatment of patients being fed by probe directly into the digestive tract. The researchers have recommended that if a patient satisfies one or more of these criteria, they should not be administered probiotics. A similar trial in Czechia has been stopped.

It had been thought that the administration of probiotic bacteria would raise the patients’ resistance to detrimental bacteria colonizing the gut.

Not surprisingly, the main manufacturers of probiotic cultures have reacted strongly, stating that there is no evidence that feeding of probiotics has a deleterious effect on healthy individuals. They have also claimed that the bacteria in the study are different from those in their own products.

I’m sure we haven’t heard the last of this, but in the meantime I suggest that normal, healthy adults should continue eating their probiotic-containing yoghurt or drinking their daily dose of probiotic cultures. The benefits of probiotic bacteria have been known for many years and countless people have consumed them without apparent ill effects. Extrapolating from patients who were already seriously unwell to normal healthy individuals is ill advised.

This morning my muesli and strawberries tasted just great with the addition of probiotic yoghurt!

Hazardous Home-made Ice Cream

2008-01-22T12:42:00.000-08:00

We’ve probably all eaten and enjoyed home-made ice cream at some time in our lives. It can be great fun for kids to help Mum make it during the summer holidays.

During the recent summer holiday (Southern Hemisphere), my neighbour gave me a recipe for making ice cream. It seemed simple enough – just combining eggs and cream, vanilla and sugar and then freezing it, stirring at intervals. “The children just love it”. There was no mention of pasteurization, which made me uncomfortable.

I looked for “Ice cream home made” on Google and found many recipes, some of which used eggs. Some included heating steps, some didn’t. This is worrying.

Eggs can potentially be infected with Salmonella during formation in the hen. External contamination can also occur, which may be transferred to the egg contents when the shell is cracked. The egg industry has procedures in place to minimize these risks and commercial egg pulp is pasteurized. This is a fairly delicate balance between providing sufficient heat to kill pathogenic bacteria and not causing the egg proteins to denature.

If you are going to make ice cream at home this summer, I recommend that you either use a recipe that does not call for eggs, or that you use a process that heats the eggs. A typical recipe can be found at:
http://www.cooks.com/rec/doc/0,1613,150189-248198,00.html
where the following instruction is given: “In heavy 3 quart saucepan with wire whisk, combine sugar, flour and salt. Beat in milk and eggs until well blended. Cook over medium low heat, stirring frequently, until mixture thickens and coats spoon, about 30 to 45 minutes. (Do not boil or mixture will curdle.) Cover surface with plastic wrap; cool completely, about 3 hours”.

The temperature of the egg mix needs to get high enough to kill Salmonella bacteria if they are present. This can be achieved by heating the mix to 80C and holding it for 15 seconds.

Botulism is back

2008-01-14T18:05:00.000-08:00

Botulism is back in the news. The US Food and Drug Administration has announced that a canning company in Michigan is recalling certain lots of canned beans. The reason given was that these particular batches of product were not adequately heated during the processing.

As I wrote in “Deadly Poison in the Kitchen” on 5th September last year, the testing of canned foods for Clostridium botulinum is impractical. No sampling plan could detect the very low level of faulty cans that we accept. We are therefore totally reliant on the correct delivery of the thermal process by the manufacturer. Not surprisingly, the regulations covering the processing of Low Acid Canned Foods* are tight and specific.

The cans must be heated in a pressurized vessel called a retort at temperatures greater than 100C (the temperature of boiling water) because the C. botulinum spores are very heat resistant. They can survive for longer than 4 hours in boiling water. Full records must be made of the process, using special controllers and monitoring instruments. The retort operator must sign these records as soon as the cooking process is completed and they must be inspected and signed off by a responsible member of Management within 24 hours.

I don’t know the details of the investigation, other than the information provided in the FDA announcement (http://www.fda.gov/oc/po/firmrecalls/newera01_08.html). However, it does appear that the procedures mentioned above were not followed. The FDA announcement, quoting the company, stated that the recall was made “because a records review identified the possibility that a small number of cans from each lot may not have been adequately cooked”. These cans should not have entered the distribution network until after the processing records had been inspected.

For the benefit of anyone who has concerns about the hazards of handling foods thought to be contaminated with the toxin (botulin) I have quoted the FDA release verbatim below:

“Any food that may be contaminated should be disposed of carefully. Even tiny amounts of toxins ingested, inhaled, or absorbed through the eye or a break in the skin can cause serious illness. Skin contact should be avoided as much as possible, and the hands should be washed immediately after handling the food. Customers who have the product or any foods made with these products should throw them away immediately. Double bag the cans in plastic bags that are tightly closed, then place in a trash receptacle for non-recyclable trash outside of the home. Restaurants and institutions are encouraged to assure that such products are only placed in locked receptacles which are not accessible to the public. Additional instructions for safe disposal can be found at www.cdc.gov/botulism/botulism_faq.htm. Anyone with questions can call FDA at 1-888-SAFEFOOD”.

* A Low Acid Canned Food (LACF) is defined as a food packed in an hermetically sealed container, whose finished equilibrium pH is greater than 4.6 This includes, but is not limited to foods like canned beans, peas, carrots, corn etc. It is not safe to try to make these products at home and industrial production must be conducted in approved premises, using processes approved by thermal processing experts and filed with the authority (in the US this will be either FDA or USDA; in New Zealand it is NZFSA).

Vegetables and all that jazz

2007-12-18T15:04:00.000-08:00

This item properly belongs somewhere other than in a food safety blog. However, in the spirit of the festive season, I couldn’t resist submitting it.

I saw a concert advertised while I was in Hong Kong. There are lots of concerts there, but this one particularly caught my fancy. An Austrian orchestra was to perform a fusion of the most diverse music styles: contemporary music, beat-oriented House tracks, experimental electronic, free jazz, Noise, Dub and Clicks'n'Cuts, etc. on instruments made of fresh vegetables.

“The ensemble overcomes preserved and marinated sound conceptions or tirelessly re-stewed listening habits, putting its focus on expanding the variety of vegetable instruments, developing novel musical ideas and exploring fresh vegetable sound gardens”.

Apparently, the group would play carrot flutes, pumpkin basses, leek violins, eggplant clappers, cucumberophones, celery bongos and numerous other vegetables. The instruments were made by the Vienna Vegetable Orchestra before each performance and were to be cooked in a soup afterwards and served to some members of the audience. (I know that being a musician is a poorly paid profession, but surviving on Rhythm and Gruel is a tough life).

If you think that this article might be a Christmas Con(cert), go to the orchestra’s website and watch their U-Tube video: http://www.gemueseorchester.org/

Happy Christmas, everyone,
John Brooks.

Norovirus spreads fast

2007-12-10T14:24:00.000-08:00

We have all read of the mystery illnesses that strike down students in schools and universities and perhaps thought that these outbreaks were caused by overcrowding or poor cleaning in these establishments.

The importance of properly educating food handlers has been emphasized once again. Workers at a Michigan restaurant displayed an almost unbelievable ignorance of simple food handling rules in January last year. (Warning: those with a weak stomach should receive guidance from a food microbiologist before reading further).

Three staff reported for work at the restaurant even though they were suffering intestinal illness. The US Centre for Disease Control and Prevention reports this in a summary of findings of an investigation released two weeks ago. One of the workers vomited into a waste bin before continuing their kitchen duties. They may have believed that using the waste bin was OK, but obviously didn’t think about aerosol generation, transfer of infective particles by their hands and contamination of surfaces in the kitchen and washrooms (or even plain old aesthetics).

The infection turned out to be a Norovirus. These viruses are highly contagious and have an infecting dose as low as 10 particles. The efficiency of infection may be as high as 93% of those people exposed. That’s why we see these outbreaks spread like wildfire through student hostels. The normal transmission pathway is the faecal-oral route, but the particles can survive on surfaces for up to four weeks, so washrooms used by sufferers become very hazardous. The particles can be killed by chlorine (bleach) solutions, but the quaternary ammonium compound used on cleaning cloths in the restaurant was thought to be ineffective.

The CDC recommended that after a vomiting event like this, all exposed food, paper serviettes, takeaway containers and straws should be discarded. All surfaces within an 8-metre radius and all washrooms should be disinfected with a chlorine solution. I would also rewash all crockery and cutlery. It was suggested that restaurant owners should consider briefly closing down for complete cleaning after someone has vomited in the facility. Staff training is critical. Part of the training should be an injunction to stay away from work for at least three days after gastrointestinal illness (and not to handle utensils or ready-to-eat foods for a further three days). Rigorous hand washing and segregation of raw and cooked foods is another obvious precaution.

You can find more information on Norovirus at:
http://www.nzfsa.govt.nz/consumers/food-safety-topics/foodborne-illnesses/
norovirus/factsheetnorovirusv2.htm

Hand washing not allowed

2007-10-31T18:27:00.000-07:00

I hope that all of us in the food industry know just how important hand washing is. If done properly, using hot water and soap, working on all the fingers and paying attention to nails, then rinsing and drying thoroughly, it can significantly reduce the amount of bacterial contamination on the hands. Indeed, there is evidence that clean hand contact with food is far less hazardous than contact from a gloved hand if the operator is not careful about glove use.

Rotavirus infections are highly contagious and commonly affect young children. The main symptoms are watery diarrhoea and vomiting, carrying the risk of dehydration. The outbreaks are often seen in kindergartens and schools. As with all gastrointestinal infections, the main route of infection is directly from improperly washed hands or through contact with contaminated surfaces and toys. The virus is resistant to the environment and to disinfection and will survive on surfaces for a long time, so toilet facilities used by children with watery diarrhoea are obvious transfer points. The time between infection and appearance of symptoms varies from 1 to 3 days.

OK – so what set me off on this lecture? My daughter in law has just had a new baby and we are obviously very aware of the potential for infection during her first few weeks of life. My son, (he’s an engineer but grew up being indoctrinated about food safety) informed me that there is an outbreak of diarrhoea at his children’s school. He has provided the girls with an alcohol hand wash to use at lunchtime, because apparently the children ARE NOT ALLOWED TO WASH BEFORE LUNCH. What kind of education for life is that?

Guaranteed safe (?) At what cost?

2007-10-17T16:28:00.000-07:00

You may have read of the shocking toll taken by Escherichia coli O157:H7 in the U.S. and the apparent increasing incidence of the disease. E. coli O157:H7 infection often causes severe bloody diarrhoea and abdominal cramps that may last for 5 to 10 days. In some people, particularly young children and the elderly, the infection can also cause haemolytic uremic syndrome (HUS), in which the red blood cells are destroyed and the debris causes kidneys failure. About 8% of patients may develop HUS. Sometimes the patients recover after a long illness, but a significant number of children have required kidney transplants.

Topps Meat Company, a US company specializing in manufacture of frozen ground beef, initially recalled 330,000 pounds of beef hamburger patties because of E. coli contamination. There had been a number of cases of O157:H7 infection tied to its products. On the 29th September, the company extended the recall to 21.7 million pounds of ground beef, bringing the total recalls in the U.S from April this year to over 30 million pounds of red meat, mostly hamburger. A week later, the company announced that it was going out of business, citing inability “to overcome the reality of a recall this large”.

Clearly, 21.7 million pounds is more than a single day’s production, so there is some sort of systemic failure in the plant. An inability to identify unique batches of product probably contributed to the size of the recall. The USDA also cited the company for “inadequate process controls in the non-ground meat production line”.

The recall highlights the problem of regulations based on product testing. In the US, E. coli O157:H7 is regarded as an adulterant; there is zero tolerance for its presence, so if it is found, the whole product lot must be withdrawn. However, it is extremely difficult to demonstrate total absence of a micro-organism from a product – even with large numbers of samples, it is highly likely that a low-level non-homogeneous contamination would be missed. I am told that the product in question had actually passed two levels of testing and that the recall began only when consumers became ill.

The problem is compounded by the predilection of Americans for consumption of hamburgers cooked rare. Doug Powell at Kansas State University has said many times (and again today) that colour is a poor indicator of sufficient cooking and that consumers should use a meat thermometer. Nobody should be made ill by the food they consume and no company has a right to claim that their small size should exempt them from running properly controlled safe production processes, but consumers must take some responsibility for their own safety. At least one of the consumers who contracted the O157:H7 infection admitted that she had cooked the burgers until they were pink inside.

Raw ground meat is inherently hazardous – it is manufactured from animals that may carry bacteria capable of causing human disease. It is almost impossible to guarantee that some of these bacteria will not be found on the carcase. When the meat is ground, the exterior surfaces and interior tissues are all mixed together, spreading the contamination throughout the meat. (That’s why you can cook a steak rare and produce a beautiful, safe meal, but cooking ground meat rare can leave the pathogens in the centre undamaged and capable of causing illness).

The whole thing is getting out of hand in the US. Companies are recalling huge amounts of food, the authorities are closing processing plants, lawyers are suing for massive damages and consumer advocates are calling for guarantees that food is safe. The result can be only a loss of confidence in the food supply and an increase in costs to the consumer. I see some parallels developing in the case of Campylobacter in poultry in New Zealand

From the industry point of view, the answer lies in greater process control based on a thorough risk analysis, not on discredited end product testing.

It’s not rocket science, but…..

2007-09-16T14:29:00.000-07:00

How many times do we hear that expression? And anyway, who decided that rocket science should be the datum for the rest of us? The success rate in that field could be improved a lot!

I want to show that simple experiments can be valuable.

Food poisoning doesn’t seem to be going away, in spite of the many articles published, television advertorials and the plethora of antibacterial cleaning agents on the market. The current concern about fresh poultry being a source of Campylobacter in the kitchen has lead to dishcloths being suggested as potential vectors of cross contamination. We all know this already, but we continue use them. Can we make them safer? Should we move to paper towels (not always convenient and perhaps environmentally unfriendly) or should we take the more expensive approach using cloths but discarding them more often? Should we boil them or put them in the dishwasher?

Standard fabric cloths were used in the kitchen for a week in the normal way. The cloths were then cut up and Standard Plate Counts were performed on Plate Count Agar. The samples were then treated by one of the following: economy wash cycle with a mdium load of dishes in a dishwasher; microwaving for 20 seconds on high (1 Kw); washing in hot water containing dishwashing detergent, or treating with hypochlorite solution containing 200ppm free chlorine. The samples were then counted again. Four complete replicates were performed. The results are shown below as a graph of log(APC/g) vs treatment; the error bars represent one standard deviation.

We can take several important points from these results:
• Used for a week, dishcloths become “microbial zoos” and a major source of contamination in the kitchen when the cloth is used to wipe benches etc.
• Hot water washing has little effect on the population size
• Bleach reduces the count by a factor of only10, probably because it is rapidly inactivated by the organic materials
• Dishwashing reduces the count by about 100x
• Microwaving is apparently the best treatment, reducing the count by a factor of over 1000x but there is still a very large population present, which can be spread around the kitchen.

This was a simple experiment that shows us some very important facts about the safety of everyday items in our food preparation areas. It might not be totally original, but that doesn’t affect the interpretation.

Who was the non-rocket scientist who made these measurements? The experiment was planned and conducted by Elisabeth Bakker, an eleven year old schoolgirl in Palmerston North, New Zealand, who submitted her research for a science fair project.

Deadly Poison in the Kitchen - updated

2007-09-05T16:29:00.000-07:00

February 29, 1984, was an unusual day for New Zealand – it was leap year and the date when the country’s first ever cases of human botulism were confirmed.

Botulism is quite rare in the developed world, (fewer than 200 cases of all forms of botulism are reported each year in the United States) but not a new disease. Emperor Leo VI of Byzantium forbade the eating of blood sausages because the link between their consumption and the disease was recognized. However, it was not until 1895 that it was understood that the disease is caused by the growth of bacteria in the food. Clostridium botulinum can produce one of the most deadly toxins known to man. The toxin is so potent that the lethal dose for humans is approximately 1 μg/Kg body weight.

In the last year there have been several cases of intoxication by foods containing botulin toxin reported around the world – a man in Ireland became ill after eating food sent to him from Poland; bottled carrot juice caused several cases in apparently related incidents; canned chili, stew, hash and other foods were withdrawn from sale after an outbreak, but several days after the recall, the products were still on sale in stores.

In all these cases, the basic rules of food production and distribution had been ignored, or someone had failed to take proper care of the food. The isolated Irish case was probably the result of unsterile food being packaged in an airtight container, resulting in growth of the strict anaerobe C. botulinum and hence production of toxin. In the other cases, the foods were commercially manufactured. The carrot juice may have been pasteurised, but this will not destroy spores of C. botulinum, so the product required refrigeration; the canned products were all low acid foods and should have received a 12D* thermal process, which is sufficient to kill spores and sterilize the product. If this had not been properly delivered, or there had been post-process contamination, spores could have survived and germinated. As for the product remaining on the shelves after the recall, the only comment I can make is that the recall process was flawed, someone was grossly negligent or totally unscrupulous.

One final point: testing of canned foods for C. botulinum is impractical. No sampling plan could detect the one in 10^12 (a 1 followed by 12 zeros) faulty cans, so we are totally reliant on the correct delivery of the thermal process. The fact that the only case we have seen in New Zealand was caused by home-preserved food shows that our canning industry is getting it right.

* A 12D process is one designed to reduce the population by a factor of 10^12. In the case of low acid canned foods, such as canned meats or vegetables, this heating process is based on killing the spores of Clostridium botulinum.

Since I wrote this article, residents of Florida have been advised to throw out products manufactured by Gourmet de Lyon. This company produces food products from a kitchen in a Delray Beach restaurant that has no permit to produce or sell canned products or those sold in jars. It would be fair to say that many of the C. botulinum cases seen in developed countries are caused by consumption of low acid canned foods produced by unlicenced manufacturers or home-canned goods sold illegally. The problem stems from the inability of such producers to control the process sufficiently accurately to ensure the destruction of the C. botulinum spores, which are highly resistant to heat.

For more information on the Florida case, see Bill Marler's website:
http://www.foodpoisonblog.com/2007/12/articles/
food-poisoning-watch/florida-botulism-risk-from-canned-products/index.html

Please ensure that you enter the whole address.

For the second time of asking: "Should I eat the chicken?"

2007-08-11T17:32:00.000-07:00

Over the last eight months we have heard a lot in New Zealand about the dangers of Campylobacter and poultry. Some of it has been well-informed and some has been blatant scaremongering that served only to confuse and frighten the consumers. The poultry industry was accused of producing New Zealand’s cheap and dirty food. Ad hoc solutions were advanced that would in all probability increase the cost of poultry in the market place without giving any guarantee that the rate of Campylobacter infection in the population would decrease.

The still small voice of reason is now being heard and concrete steps are being taken to understand and reduce the problem, which is not unique to New Zealand*. The New Zealand Food Safety Authority is studying possible control measures. Researchers at Massey University are examining isolates from the environment and from patients, building a comprehensive database on Campylobacter strains that can be used in epidemiological studies. The first version of the Poultry Industry Association of New Zealand Broiler Growing Biosecurity Manual has now been released. This is a comprehensive manual of approved procedures aimed at controlling infection and spread of Campylobacter in poultry flocks. When fully implemented, the procedures should greatly reduce the incidence of Campylobacter in poultry in the market place. The production of the manual is a creditable response of the PIANZ to the concerns expressed by scientists, politicians and the general public.

So does that mean that campylobacteriosis in New Zealand is under control? I don’t think so. I believe that it is highly unlikely that Campylobacter can be eradicated in poultry, at least in the short term. There are also other sources of the bacteria in our food supply and in the environment. Only a couple of weeks ago, a number of mountain bikers taking part in a contest became ill with campylobacteriosis. No food source could be identified as the source; infected surface water and mud, which had covered the competitors as they splashed through the puddles, was blamed as the source.

Distributors, wholesalers and retailers, together with the consumers themselves, must take some responsibility for the safety of food. Even though campylobacteriosis has been shown to be linked with consumption of undercooked barbecued chicken, I am not convinced that New Zealand’s high incidence of the disease can be attributed entirely to this cause. There are many routes of infection for the consumer. Leaking packages in display cabinets can contaminate other food purchases, the hands of customers and the handles of supermarket trolleys. Cross contamination in the restaurant or domestic kitchen via utensils and chopping boards may result in salads or other uncooked dishes becoming infected. The dose of bacteria required to initiate the illness in humans may be only a few dozen cells. This means that commercial and domestic food handlers must be properly educated in practical food hygiene and food safety. We can all contribute to the safety of our food.

Should we eat the chicken? You bet!

* Work conducted in Hong Kong by my team showed that between 50 and 60% of fresh chicken was contaminated with Campylobacter. This dropped to about 30% if the poultry had been frozen. These rates of contamination are entirely consistent with figures reported for other countries.

Coliforms and Faecal Contamination

2007-07-18T21:38:00.000-07:00

I recently read a newspaper article about the potential contamination of ground water from failing septic tanks. Sanitarians had found septic tank systems close to a restaurant that might be feeding human faecal matter to the ground water. However, wells in the surrounding area, both up and downstream of the potentially contaminated site tested negative for Escherichia coli. The significance of this finding is that the sanitarians could not demonstrate that the wells were in fact contaminated by human faeces or the outflow from the septic tanks.

Escherichia coli is a bacterium found in the intestines of man and animals, but it doesn’t grow in water and doesn’t grow well in the environment. So if it is found in water, the implication is that the water has been contaminated with faecal material. Some strains of E. coli, such as O157:H7, cause serious disease, though most do not. The micro-organism is used as a Faecal Indicator. The importance of finding any E. coli in water or food is that other enteric pathogens, such as Salmonella or Norovirus, might be present.

The article went on to say that 28% of the wells tested did contain “coliforms” and this indicated that the water system was at risk of more serious contamination. This is probably correct, because a properly constructed well should draw water from deep in the ground; such water has often been in the ground for hundreds of years and has been filtered through the soil and should have a low bacterial count. Though the article was correct, it may have caused some confusion in the mind of the reader.

The finding of coliforms in water is not necessarily indicative of danger. The coliform group is defined by the tests* that we use, i.e. “coliform” is not a species, it simply says that these organisms give us a positive result in the tests we apply. This means that some bacteria are included in the group that have no faecal connotation at all. These bacteria may be found in plant material that has never come in contact with faeces of man or animals and the bacteria may even be transmitted in the seeds of the plants. So if we find coliforms in the water or in food, it is not a cause for immediate panic. Obviously, if we find large numbers present, we should look to find out why. The well may be affected by inward leakage of surface water; fresh salad vegetables may have these micro-organisms present at low numbers on their tissues, but high numbers suggest poor kitchen hygiene or temperature abuse.

If we wish to demonstrate that contamination by faeces has occurred, we need to do further tests on the bacteria to see if they are actually E. coli. The tests involve different culture media, different incubation temperatures and biochemical tests.

*The tests that we use to detect coliforms vary somewhat between countries. The tests are based on the ability of coliforms to grow in the gut, so they must be able to grow in the presence of bile salts. Bile salts are secreted into the intestine to aid in digestion of fats; they are natural detergents. So some media formulations include bile salts, while others employ synthetic detergents. The media also contain lactose as a carbon and energy source for the bacteria and the tests are incubated at the optimum temperature for the growth of the target organisms. So the coliform group is defined by their ability to produce a positive result:
Acid and gas production in 24 to 48 hours from lactose at 37C in the presence of bile salts.

If we wish to demonstrate that Escherichia coli is present, then we may subculture into a similar medium containing selective agents (which prevent other similar micro-organisms from growing) and raise the temperature to 44.5C and again look for gas production. At the same time we may look for the ability of the micro-organisms to convert tryptophan to indole; produce sufficient acid to change the colour of methyl red pH indicator; produce acetoin from glucose and grow on citrate as the sole carbon and energy source. This series of tests is known as the IMViC tests. E. coli normally gives a "++--" profile. Finally, we may grow the culture on Eosin Methylene Blue agar and look for the formation of a metallic green sheen. If all these tests give the correct result, we can be pretty sure that E. coli is present and faecal contamination has occurred.

Free Choice or Safety of the Population?

2007-06-03T19:05:00.001-07:00

Governments and regulators are always in a difficult position. Do they allow total freedom of choice, or does their responsibility to the population require them to make restrictive decisions based on the greater good of the people? The government then performs a balancing act, running the risk of being labelled as Big Brother (or at least Nanny Government) or as being irresponsible. For example, should we all be allowed to use any chemical we can obtain to relieve the monotony of our daily lives, or should there be regulations to control the use of mind-altering substances and thus protect us from ourselves? If we allow unfettered use of any substance and thus maintain personal freedom, how do we protect the innocent - those who are too young or too poorly educated to know that these materials may be harmful?

Most people would probably come down on the side of some restrictions for the use of drugs, though some would argue for freedom of choice. The same applies to the sale and consumption of raw milk and raw milk products.

I have discussed raw milk before in this blog. I might have left it at that, but the New Zealand Government, in the form of the New Zealand Food Safety Authority has now called for submissions on a proposal to permit direct imports of Roquefort, a soft raw milk cheese made in France, and extra hard Parmesan-style raw milk cheeses Grana Padano, Pamigiano Reggiano, Romano, Asiago and Montasio. An extensive programme of risk assessment has already been undertaken and the Authority is now consulting with industry groups.

This development may lead some members of the community to believe that Big Brother has been wrong all along and is now backing down. Extra hard cheeses have a low water activity* of about 0.693 that prevents the growth of most bacteria. Soft cheeses, such as Brie, Camembert and Roquefort have much higher water activities and thus may permit the growth of pathogens such as Listeria monocytogenes (see post To Pasteurize or not? - 10th December 2006). The truth is that cheeses made from raw milk are not as safe as those made with pasteurized milk.

European Community (EC) legislation sets microbiological, food safety and process hygiene criteria that reduce the risks in consumption of raw milk cheeses. NZFSA has recommended that if these products are to be directly imported and ultimately manufactured in New Zealand, additional risk mitigation measures should be introduced:

• 100% verification of certificates attesting that the relevant EC standards have been met

• continuing monitoring of products to check for E. coli levels, which can indicate unsafe manufacturing conditions leading to faecal contamination of the cheese.

It is expected that leaflets, posters and point of sale brochures will be required to educate the consumers on the risks of eating cheeses made from unpasteurized milk and that labelling of the products will be mandatory. Yet another acronym has been added to our lexicon: YOPI - Young, Old, Pregnant or Immunocompromised. This group of the population should not consume raw milk products.

*Water activity is a measure of the ability of water to take part in biological and chemical reactions. It is measured as a ratio of the partial vapour pressure of the food to that of pure water. That sounds complicated, (it's not) but it results in a scale of water activity running from 0 to 1. Generally speaking, the lower the water activity, the harder it is for micro-organisms to grow. Water activity in foods can be controlled by salts and sugars. So we can formulate food to have a particular water activity and thus preserve the food.

Yet more on unpasteurized milk

2007-03-18T18:40:00.000-07:00

This post was updated on 30th April, 2007.

In the previous post I mentioned the potential for contraction or spread of disease that could result from the consumption of raw milk or products made from unpasteurized milk. In that case the consumers may have contracted salmonellosis from the milk.

This week the Grey Bruce Health Unit in Ontario, Canada, issued a press statement, warning pregnant women to avoid consumption of raw milk and unpasteurized dairy products. The warning was issued to help prevent listeriosis infection in newborn babies. The original release can be found at:
http://www.publichealthgreybruce.on.ca/HOME/NewsEvents/2007/Mar/2006Mar14_Infant-Listeriosis.htm

Non-pregnant humans are highly resistant to the infection, though if they do become infected, the symptoms can be very serious, including meningitis and sepsis (invasion of the blood or tissues by bacteria or their toxins). Pregnant women may contract Listeriosis, but show no serious symptoms beyond mild influenza-like signs. Their foetus, however, may be infected, resulting in abortion or stillbirth. If the infant is infected during delivery, symptoms of meningitis begin 1 to 4 weeks later.

The Grey Bruce Health Unit news release stated that it had received a laboratory-confirmed report of an infant who contracted the disease. The most likely source of infection was said to be the mother’s consumption of raw milk cheese.

The release went on to say that pregnant women are at a 17 times higher risk than the general population of contracting the disease.

My personal and professional opinion is that any perceived benefits of drinking raw milk are far outweighed by the risks, both to the individual and to others in the same household. This is supported by scientific evidence: In the last decade the Center for Disease Control and Prevention has documented more than a thousand cases of food-borne illness and two deaths, all caused by unpasteurized dairy products. I have advised my pregnant daughter-in-law to avoid raw milk and raw milk products.

More on unpasteurized milk

2007-03-04T13:16:00.000-08:00

The arguments about the desirability or otherwise of drinking unpasteurized milk continue. It seems that its proponents will hear nothing said against the practice; many scientists and doctors provide comment, often supported by case studies, that suggest that there are significant and serious risks associated with drinking unpasteurized milk.

The following report was posted recently on the Food Safety Network mailing list on behalf of Doug Powell of Kansas State University:
Begins
http://www.wdbj7.com/Global/story.asp?S=6170552&nav=S6aK
WDBJ7 News
HARRISBURG, Pa. -- The Pennsylvania Health Department is, according to this story, warning consumers not to drink raw milk from a York County dairy farm after confirming that two people who drank it last month were sickened by salmonella.Health Secretary Calvin Johnson was cited as saying the state Agriculture Department has also obtained three samples from Stump Acres Dairy in New Salem that tested positive for salmonella.
Ends

Of course, the facts that two consumers of the product contracted salmonellosis and that samples taken from the dairy tested positive do not prove that the unpasteurized milk was the source, though detection of the same serotype in patients and the milk would be very strong evidence. However, the correlation between raw milk consumption and illness is hard to ignore.

There are sometimes suggestions that the pasteurization process is too severe. The process was originally designed to eliminate Salmonella, but was later modified to be slightly more rigorous to ensure that Coxiella burnetti (a rickettsia-like organism which is the cause of Q-fever - a febrile disease of man and which sometimes has serious sequellae), was eliminated. There is currently some investigation of the time/temperature relationships in milk pasteurization to see if there is a possibility of making the process less severe.