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:

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

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:  

It is available on-line at:

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". 

Sunday, December 18, 2016

It's that time of year again!

Many readers will have noticed that my posts are less frequent than before I retired.  Nevertheless, I do keep an eye on food safety matters in the news media, and the number of page views each day is relatively stable, with total of around 278k over the years.  This suggests to me that the blog is still fullfilling its original purpose and that the interest in safety of food is undiminished.

The Christmas holiday is fast approaching and, in New Zealand, this is the time for parties and barbecues.  Food is often prepared in advance and may be displayed for some hours outside.  The potential for contamination and temperature abuse is probably higher than at any other time of year.

If you are serving sliced ham or other meats, please remember the safety message: Clean, Cook, Cover, Chill.  Minimise hand contact with cooked food and be careful not to handle raw meats in a way that can allow cross contamination of cooked foods.

If you are cooking on a BBQ, make sure that the meats are cooked through.  I wrote a similar message in 2014.  I use a meat thermometer to check internal temperatures, as you can't determine if meat is properly cooked by its appearance.  "When the juice runs clear" is not a reliable way of ensuring that chicken is properly cooked.  If you have any doubts, please read the earlier post.

There is nothing wrong with leftovers, provided that the food is refrigerated and eaten within 24 hours.  But please remember that leftovers from a party are more likely to have been temperature abused and may have been picked over by your guests, including children.  Are you totally confident of their hand hygiene?  If you are reheating leftovers, ensure that the temperature rises to at least
75 C.

Thank you all for your continued interest in Safe Food.  I wish you all a very happy and safe Christmas holiday.

Tuesday, October 25, 2016

Hazards of a long supply chain - sale of time-expired product

Poor old Fonterra!  The New Zealand dairy giant is in the news again for a problem with milk powder in China, but this time it could have been any food company.  Its product has been on-sold several times, and time-expired milk powder has been repackaged and sold at a discounted rate.

I haven't been able to find out whether the original powder packaging was marked with a "Best before" date, or a "Use by" date and these terms are not used in China.  According to National Standard GB7718-2011, the General Rules for the Labeling of Prepackaged Foods, in China, the labeling consist of production date and date of minimum durability.

Clearly, Fonterra is blameless in this case, and, with a long supply chain, it is difficult for the company to control what happens to its product.

The obvious concern in China, beyond any illegal activity, is the potential hazard to the consumer.

Can time-expired milk powder be hazardous to the consumer?  In my opinion, this is highly unlikely.  Properly packed and stored milk powder will keep for years - bacteria will not grow in the very low water activity in the powder.  However, repackaging offers the possibility of contamination.  The most likely issue is that the powder may become oxidised, leading to taste defects.

So, is this a big deal?  Yes - the consumer is entitled to receive food products in good condition and not be sold inferior goods, and this includes not receiving perfectly safe but time-expired products.

Friday, September 2, 2016

FDA gives manufacturers 1 year to remove certain antibacterials from hand soaps

I have written previously about the undesirability of including antibacterial chemicals in hand washing soaps

In late 2013, FDA gave soap manufacturers a year to demonstrate that adding the antibacterial chemicals triclosand and triclocarban to "antibacterial soaps" had any benefit, compared with regular soaps, in terms of preventing illness and the spread of certain infections.

It appears that insufficient information was provided to FDA to convince the regulator, and so manufacturers now have a year to remove these ingredients from their products.

The new regulation does not currently affect chemicals including benzalkonium chloride, benzethonium chloride and chloroxylenol.  It also applies only to hand soaps and body washes.  It does not apply to toothpaste, for example.  It also doesn't apply to hand sanitizers, such as alcohol preparations, and products intended for use in hospitals, etc.

So, what are we to do?  The simple answer is to continue hand washing with regular soap - it's just as effective as "antibacterial soap".

Saturday, August 6, 2016

Expert comment on potential hazards of oxidised fish oil

Scientists are often misunderstood and maligned by the general population and by writers of popular diet and health articles.  However, within the scientific community, publication of research and critical evaluation by other scientists is the norm, and leads to greater understanding of our health and wellbeing.

My friend and colleague, Dr. Laurence Eyres, is a fats and oils chemist.  He has written the following article on studies concerning oxidised fish oil.  

Oxidised Fish Oil
The authors of a controversial fish oil supplements paper have published another paper on the potential deleterious effects of oxidised fish oils. This has now been picked up and blown out of context by The Listener in New Zealand (Week July 30-August 5).

The wider lipid scientific community were surprised and highly disappointed by the original early 2015 Nature Science Reports (NSR) paper by the University of Auckland.  The Therapeutic Goods Authority of Australia (TGA) performed follow up analyses, and all Australasian (ANZ) oils were not oxidised, and Omega-3 content met label claims. Earlier ANZ studies had reported similar findings but were not cited by the NZ authors.  These results have been communicated to NSR, and journal feedback is still being waited on.  The TGA took no actions against ANZ manufacturers, once again in keeping with the wider view that the fish oil products were meeting their omega-3 claims and were not heavily oxidised.

The justification for the new paper appears to be driven / justified by the NSR paper, which we refer to above.  This NSR paper remains in the strongest doubt/dispute.  The new paper uses heavily oxidised oil that the NZ authors prepare.  As ANZ fish oils are NOT oxidised, the study is seen as not relevant.  This is the view of many scientists who have seen the new paper.  The peroxide value (PV) result of the oil, indicating primary oxidation, is exceptionally high, further indicating that the use of such an oil is not relevant.  The dose used is equated to 40 mL per day for a human consumer.  This dose is seen as exceptionally excessive.  Few consumers would be taking more than 1-3 g per day. Nutritionists would advise increasing the level of Vitamin E if high levels of polyunsaturated fatty acids are used for feeding any mammal.

The unoxidised oil actually and interestingly shows improvement in the new paper versus the control treatment, although little is stated by the NZ authors on this aspect. Also the unoxidised oil had improved survival rates in the studied rats, and so whilst we totally agree that women who are pregnant should not consume rancid oils, they do need omega-3.

This author spoke about oxidised lipids at the recent NZIFST conference.  The oils and fats group has held several seminars on the toxicity of oxidised fat over the years and it has been a stance of ours that we should not consume any oxidised oils. There are many other significant sources of oxidised fats in normal human diets other than fish oil. These include used and abused frying fats, bottled oils and rancid nuts such as walnuts. The topic of toxic aldehydes from such highly oxidised fats was covered in a recent issue of Inform magazine.

The authors in their introduction state “that in animal models, exposure to oxidised lipids has been shown to cause harm, including growth retardation, organ toxicity, and accelerated atherosclerosis.  However, the effects of consuming oxidised lipids during pregnancy are unknown. For this reason, this latest study was designed to investigate the effects of fish oil supplementation during pregnancy on the adult offspring of rats fed a high-fat diet, and they also included oxidised fish oil groups. As obesity is associated with increased oxidative stress and greater production of oxidised lipids, the effects of an oxidised lipid supplement may be more marked in obese mothers. 

The study is very interesting and will be probably the subject of more media hype.  However, a couple of comments. The fish oil (unspecified as to composition) was oxidised artificially to really highly rancid and toxic levels and then used in the rats at levels 20-40 times a normal human dose.

Any relevance to the consumption of omega-3 supplements in humans is likely to be none.