Wednesday, December 31, 2008

Is food less safe these days? Part 1

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

Sunday, September 21, 2008


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.

Saturday, August 23, 2008

Exercise viewed from the relative safety of the couch

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
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

Friday, August 22, 2008

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

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.

Wednesday, August 13, 2008

Coming soon to a store in New Zealand?

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

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

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.

Sunday, June 8, 2008

Tuberculosis and Mexican cheese

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

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

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.

Thursday, June 5, 2008

It had to happen!

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.

Tuesday, May 6, 2008

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

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.

Saturday, May 3, 2008

Is hamburger a greater risk for E. coli?

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

Monday, April 21, 2008

What interests you most?

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.

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

Friday, March 28, 2008

The news just keeps on getting worse!

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:

Pigeon pie, anyone?

Monday, March 10, 2008

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

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.

Sunday, February 10, 2008

Campylobacter jejuni - SEM image

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

Saturday, February 9, 2008

That Campylobacter problem – it just doesn’t go away

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

Sunday, February 3, 2008

Dangerous probiotics? Probably not

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!

Tuesday, January 22, 2008

Hazardous Home-made Ice Cream

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:,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.

Monday, January 14, 2008

Botulism is back

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 ( 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 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).