Tuesday, December 12, 2017

Wild meat and botulism? Confusion reigns.

Recently in New Zealand, a family became seriously ill after consuming wild boar.  Authorities have said that the meat is suspected of being contaminated with botulin toxin.  Botulin is one of the most toxic substances on the planet.

I am somewhat confused by the reports - botulin toxin is produced by Clostridium botulinum growing in very low oxygen conditions.  The toxin is heat labile, i.e. it is destroyed by heating.  Apparently, the family ate curry made with the meat, and I would have expected the toxin to be destroyed by the cooking.  The family was reported to have collapsed within minutes of consuming the meal.  I'm not going to be dogmatic about this, but the toxin acts by binding to the nerve synapses, preventing release of actyl choline and thus blocking nerve impulse transmission.  Absorption of the toxin in the gut and transport to the synapses normally takes several hours, so the reported immediate collapse of the family is surprising.   As far as I am aware, there is no information on how long the cooked curry was held before consumption.  Spores of C. botulinum are extremely heat resistant, so if the curry were kept warm for a length of time before consumption, the spores could have germinated and produced toxin, though this implies quite a long time between cooking and consumption.

Health authorities have taken samples for testing and these have been sent to Australia - the tests are not simple, and results may not be available for several weeks.  However, the family is recovering in most cases, and anti-toxin has been administered.  Normally, recovery from botulinum intoxication takes weeks or months, not days.

Meanwhile, Ruapehu District Council has issued a warning over the health and safety of hunted and home kill meat.  It is illegal to sell hunted and home killed meat, but it can be shared with family, friends and visitors.  Again, this is confusing - if it can be legally consumed in this way, then there is no safety issue; it's a matter of regulations designed to ensure that meat offered for sale has been properly processed in an approved premises.  Further confusion arises because hunted and home killed meat can be consumed on a marae for traditional activities, but commercial operations on a marae must use commercially processed meat.

It seems to me that the toxicology report must be made available before conclusions can be drawn on the cause of this disaster for the family, and that reporters and regulators should be very careful to get their facts straight before publishing statements that can confuse the public further.

Friday, November 17, 2017

More food scare mongering

I recently read an article in New Zealand Farmer entitled "The stomach-churning truth about what's in synthetic food".  The writer, Jon Morgan was writing an opinion piece and quoted an article by a British food writer, Joanna Blythman.

She had apparently investigated the ingredients in the "Impossible Burger", which has been launched in the US.  The ingredients can be found in many foods already consumed widely in New Zealand and other countries.

She was upset that the major ingredient by weight was water, suggesting that "no quality product uses it as a bulk ingredient".  I had a look in our food cupboard and refrigerator, and found many processed foods with water listed as the main ingredient.  Practically any food manufactured in which powders, such as milk powder, are incorporated will require water to rehydrate the dry ingredients.  (What does she think is the major component of a beef steak cut from a cattle beast?)

She then got stuck into some of the other dry ingredients - textured wheat protein, potato protein and soya protein isolate, claiming that these were produced using high-tech. chemical and physical processes veiled in secrecy.  The konjac and xanthan gums used in food manufacture were described as industrial hydrocolloids, the latter used in oil drilling muds.  In my opinion, this reference is totally irrelevant - there are many materials found in foods that are also used in unrelated industrial processes, such as starch used in paper coating.

The ingredient that caused Joanna the most heartache appeared to be soy leghemoglobin, which is a protein produced in genetically modified Pichia pastoris and which imparts a meat-like flavour profile onto plant-based foods.  I found a number of scientific studies that tested its safety for consumption at up to 0.8% in ground beef analogues.

Overall, I came to the conclusion that this was just another scare mongering beat up of modern food technology.  It is worth noting that Sir Peter Gluckman, the New Zealand Prime Minister's Chief Science Advisor, has stated that synthetic foods will have a major impact in 10 to 15 years, and that great strides are being made in the commercialisation of synthetic milk and meat.

I also tried to find information on Joanna Blythman's qualifications to comment on the safety of foods.  All I can find is that she graduated from City, University of London.  City is focused on business and the professions, so I can only assume that she has no food or science qualifications (if she does have some, then perhaps I am doing her an injustice) but at the moment, it appears that she is yet another journalist who has set up to criticise the food industry.

Sunday, October 8, 2017

Toxic shellfish - again

Once again, the collection of shellfish from a coastal area of New Zealand is subject to a warning from the Ministry for Primary Industries.  This time the affected area is most of the Taranaki coastline.

Tests on shellfish show that levels of Paralytic Shellfish Poisoning (PSP) toxins are above the safe limit of 0.8 mg/kg set by MPI. Unfortunately, the toxins are not destroyed by cooking, so the only advice is not to collect and eat the shellfish.

I have written about PSP before, so, rather than reiterate the warnings and background, here is the link to the earlier post.

Monday, June 19, 2017

Would you eat transgenic food?

Many readers will immediately respond to the title of this post with a resounding "NO".

Don't be so hasty!

Looking close to home, we find that our own bodies contain many foreign genes.  It is estimated that around 8% of the human genome consists of fragments of endogenous retroviruses - about 100,000 of them.  Not all of these fragments are "junk" (a term the popular press is rather keen on).  A number of viral genes have been co-opted for our own purposes, in gene regulation, production of transfer RNA and ribosomal RNA.  One viral gene is critical to the formation of the placenta.  

On this basis, I'm not too surprised to read a piece of research* that shows that some of our vegetable crops are naturally transgenic.  Cultivated sweet potatoes contain the transfer DNA sequences from a bacterium called Agrobacterium.  This genus naturally infects the roots of certain plants, causing a nodule or hairy roots.  This T-DNA is not present in the wild type sweet potatoes, implying that one or more traits carried on this piece of DNA were selected for during the domestication of the sweet potato.

The authors of the paper point out that sweet potatoes have been consumed for millennia, and that this "may change the paradigm governing the “unnatural” status of transgenic crops."

If we look further, in my opinion, it is almost certain that we will find other bacterial or viral genes in our fruits and vegetables.


* The article is technical, but you can find it online

The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop



www.pnas.org/cgi/doi/10.1073/pnas.1419685112 

I originally published this article in 2015 on the NZIFST blogspot:  http://nzifst.blogspot.co.nz

Friday, June 9, 2017

Hand washing is REALLY important

According to a post on Stuff, a worker at a Silver Fern Farms meat plant in New Zealand lost her job for not washing her hands.

At first sight, this may appear to be a draconian decision, but the company had written procedures in place, stating that if a worker touched dropped meat, they should wash their hands before handling other meat being prepared for packaging.  Meat that has fallen onto the floor can be contaminated by many different bacteria and by other organic material.  Handling this fallen meat and the area around the dropped meat table could contaminate the worker's hands and hence other meat being packaged.

If the worker had been properly inducted into the plant, she would have been made aware of the requirement to wash hands after retrieving meat from the floor and transferring it to the dropped meat table.

The real problem is that the company has a meat export licence that almost certainly has stringent hygiene requirements incorporated.  Thus failing to observe the written procedures in relation to dropped meat could have put the licence, and the livelihoods of all other workers at the plant, at risk.

Wednesday, April 5, 2017

Fermented foods - tasty, safe and good for you.

Recently, one of my regular readers watched a BBC television programme on 

"Which foods can improve your gut bacteria?" narrated by Dr. Michael Mosley.  She wrote and asked me  to comment on the safety of such foods, how they should be stored, plus potential risks of manufacturing them at home.


Traditional, naturally fermented foods have been around for hundreds, if not thousands, of years.  These days, we tend to relate the term "Fermented food" to sauerkraut, kimchi, tempeh, or perhaps yoghurt and cheese.  However, the Egyptians knew about wine production 5,000 years ago (though they didn't know that yeasts were involved).

Fermentation is a natural process, carried out by bacteria, yeasts and occasionally moulds, that actually preserves raw foods, often by production of acid or alcohol, which prevent spoilage.  Of course, the preserved food sometimes bears little resemblance to the original.  We enjoy these foods because the fermentation changes the flavour and texture of the raw material, often increasing the complexity.

We now know that our gut microflora, now called the gut biome, can be influenced for the better by consumption of some fermented foods.  The microorganisms that carry out the fermentation can sometimes pass through the very acid conditions of the stomach and may be able to colonise the gut wall, perhaps displacing undesirable bacteria, though some just pass through, having a transitory effect on the gut biome.  They can help with traveller's diarrhoea or lactose intolerance.

Dr. Mosley and his team investigated the claims for such benefits by setting up three groups to consume various fermented products for four weeks and looked for changes in their gut bacteria.  You can read about it in the link above.

The team also tested the products to determine the range of bacteria in them.  Home-made fermented foods tended to contain a diverse range of bacteria, while commercial products, which may have been pasteurised, often contained very few.  Thus the flavours and textures would be similar, but the potential health benefits of the microbial populations had been removed.

Over many years of teaching food microbiology, I made sauerkraut with my students.  It's an easy fermentation to carry out, requiring only finely shredded cabbage and about 2 - 2.5% salt packed in a suitable container.  Air must be excluded to prevent the growth of moulds on the surface of the kraut. We followed the fermentation daily, counting and identifying the bacteria taking part, and measuring the titratable acidity and pH.  

We always found a succession of bacteria.  The undesirables, like Escherichia coli and other coliforms disappeared within the first couple of days as lactic acid bacteria produced lactic acid and reduced the pH.  Leuconostoc  species, found on the inside leaves of the cabbage, would begin the acid production, giving way to Lactobacillu plantarum and eventually L. brevis.  The final pH of the sauerkraut is around 3, which is plenty low enough to prevent the growth of pathogens.

The kraut can be stored in the refrigerator for a short time, but must be protected from oxygen to prevent spoilage.  If you would like to make some at home, download the original recipe, written by Carl S. Pederson in 1939.  He studied the fermentation extensively over many years.  There are many other, more recent recipes available on-line and much has been published in the scientific literature on the microbiological changes that occur during fermentation.  You can also find many recipes for kimchi on-line.

Are home-made fermented vegetables safe to consume?  Yes, provided that the fermentation has produced sufficient acid to lower the pH to around 3 to 3.5, which will prevent the growth of pathogenic bacteria.  The finished product must not be allowed to go mouldy, since moulds can metabolise the acid and raise the pH to levels at which pathogens could grow.  My son, who is an electronics engineer, has successfully made sauerkraut and kimchi at home.  You don't need to be a microbiologist or food technologist to make safe, tasty fermented foods!






Saturday, March 18, 2017

Food Trash Writing



Once again, an article about fast food has been posted on several “healthy living” websites and reposted on FaceBook.  On this occasion, HealthZone.Tips writes about McDonald’s french fries under the title:
When You Find Out What is in McDonald’s French Fries, You Will Be Disgusted!

Whatever you think about fast foods, you would expect the article to be accurate and not merely sensational.  The article claims that McDonald’s puts more than ten ingredients into its fries, and quotes Grant Imahara (Myth Busters), suggesting that the fries are not really potatoes!  This article is just plain scaremongering, and I wonder what is the author’s motivation.

The post lists the main ingredients, noting that there are other components:

    Potatoes
    Canola oil
    Soybean oil
    Hydrogenated soybean oil
    Natural beef flavour
    Hydrolysed wheat
    Hydrolysed milk
    Tertiary butylhydroquinone (TBHQ)
    Dimethylpolysiloxane
    Dextrose

and states that “The three offenders on the list are TBHQ, dimethylpolysiloxane and hydrogenated soybean oil”.

Notice that there is no mention of the amounts of these “offenders” in the fries, as you would find on a food label - usually as grams per 100 grams and grams per serving. 

So let’s look at these three components.

Tertiary butylhydroquinone E319, an anti-oxidant, is used as a preservative for unsaturated vegetable oils and also for many edible animal fats.  Both the FDA and the Scientific Panel on Food Additives, Flavourings, ProcessingAids and Materials in Contact with Food of EFSA  regard TBHQ as safe when used at the permitted levels. The Panel stated that, “Based on the data reviewed, the Panel concluded that TBHQ is not carcinogenic and that further genotoxicity studies were unnecessary.  TBHQ is used in many foods and also in perfumery. In a medium serving of french fries (133 g) there is about 22 g fat and thus about 4.4 mg TBHQ.  Using the EFSA acceptable daily intake (ADI) of 0.7 mg/kg body weight for a 70 kg human, this equates to about 9% of the ADI, which itself has a 100x safety factor built in.

Dimethylpolysiloxane E900  is a polymeric organosilicon compound, used as an antifoamer in cooking oils to prevent foaming and splatter.  FSANZ permits a maximum of 10 mg/kg of the final food.  The WHO summarised a number of studies of the effect of DMPS on humans and animals with “None of these studies has revealed any significant toxicity. The metabolic studies, including those in man, indicate that the orally administered dimethylsiloxanes are mainly excreted unchanged in the faeces.”  It is difficult to obtain data on levels of DMPS in final foods, but using data from Five Guys, I estimate that the level in the frying oil could be around 0.004% and in the fries, the final level could be around 0.9 mg in a medium serving of fries, or 6.8 mg/kg fries.

Hydrogenated soybean oil  is used in the production of margarine, shortening, and salad and cooking oils.  The US FDA Committee on GRAS substances concluded that “There is no evidence in the available information on hydrogenated soybean oil that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when it is used as a direct or indirect food ingredient at levels that are now current or that might reasonably be expected in the future”.



For those readers who live in New Zealand:  I consulted a fats and oils chemist.  He told me that 
They don’t use hydrogenated soy in Nz and never have done; the oil is now monounsaturated canola/sunflower oil.  TBHQ is no longer used.  As far as he is aware, the oil blend no longer contains DMPS, and even when it was used, the level was around 1ppm.



Tuesday, February 7, 2017

Brexit, Trump and food safety fears

The decision by Britain to leave the EU would not immediately spring to mind as a cause for concern over food safety.  Neither would the election of Donald Trump as President of the USA.

However, decisions made in haste or with little forethought can often have unexpected consequences.

It now appears that a trade agreement between the US and UK might result in food products banned in the EU being imported into the UK.  This might include beef from cattle implanted with growth hormones, chlorine-washed chicken, and unlabelled genetically modified (GM) foods.

This has resulted in a furore on FaceBook, though the concern about chlorine-washed chicken is a little surprising.  Chlorine rinses are used extensively in the food industry to reduce surface contamination on vegetables, during chicken processing and for sanitation of equipment during food processing.

Of course, chlorine is also used in water treatment for decontamination of potable water supplies where UV treatment is not used, perhaps for cost cosiderations.

Over the years, a lot of work has been done on the effects of chlorine in foods.  At the levels used for practical decontamination, there is no risk to human health, though some chemical changes are inevitable. 



If you are keen to follow up on this, The Institute for Environmental and Scientific Research Limited, (ESR) in New Zealand produced a report in 2008 for the New Zealand Food Safety Authority:  
Client Report FW0883 CHLORINATED COMPOUNDS FORMED DURING CHLORINE WASH OF CHICKEN MEAT.

It is available on-line at:  http://www.foodsafety.govt.nz/elibrary/industry/chlorinated-compounds-formed-research-projects/FW0883_Chlorinated_compounds_in_chicken_meat.pdf


The report stated that "In conclusion, no safety issues were identified due to the use of chlorine dioxide and ASC for poultry carcass disinfection. Chlorination reactions appear to be insignificant for these compounds and oxidation reactions do not appear to result in significant alteration of the fatty acid and amino acid composition of poultry carcasses".   Further, the authors stated " ...we consider that there is insufficient evidence to justify further investigation of the risks to human health from the use of these disinfection chemicals in poultry processing".