It’s not quite about food safety…

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

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

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.

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

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.

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?

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/