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 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.

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 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.

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
http://foodsafetywithjaybee.blogspot.com/2007/10/
guaranteed-safe-at-what-cost.html

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. 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

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: http://barfblog.foodsafety.ksu.edu/tags/tv/).