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 entitle 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.

Saturday, June 11, 2016

Putting the squeeze on raw milk

Many of you will know that I have written several articles on the dangers of consuming raw milk.  In my opinion, any perceived benefits are greatly outweighed by the real risks.

However, if you will permit me to mix metaphors, you can now have your cake and eat it.

An Australian company, Made by Cow, is offering raw milk processed by "cold pressure".  There are few details available, but it appears that the company is using an established process (High Pressure Processing, HPP) to make the milk as safe as pasteurised milk.  The process has been approved by the New South Wales Food Authority, and the product can be sold in stores.

The concept of killing bacteria by applying high pressure has been known for many years, (Hite studied the effects of pressure on bacteria in 1899), but practical machines to process food have been difficult to build and the processes have all been slow.  

Pressures of up to 6800 Bar (about 100,000 psi) held for several minutes are required to kill bacteria. Of course, there are many possible combinations of pressure, temperature and time, and whether the pressure is applied in a single treatment or is cycled several times.  However, the degree of inactivation appears to depend on the duration of the high pressure, and not the number of cycles.

The primary site of damage to the bacterial cell appears to be the cell membrane.  If this membrane is damaged, its permeability may be greatly changed, resulting in failure of respiration and transport functions, and hence death of the cell.  Spores are very much more resistant, so milk processed by pressure alone is unlikely to be sterile.  There are some changes in foods resulting from HPP - some enzymes may be inactivated, while others have their activity enhanced.  Other effects seen in foods are the gelling of some non-enzyme proteins and enhanced browning reactions at high pressure.  One assumes that the Made by Cow patented process has overcome these undesirable changes in the milk.

The major problem with current HPP is that the machines are batch processes, so throughput is low and the products are likely to be expensive.  However, if you are adamant that thermal pasteurisation damages the nutritional and functional properties of the milk, HPP milk may be the way to go.

Monday, January 11, 2016

Do antibacterial soaps and wipes have any effect on antibiotic resistance? Should we use them in the home?

Over the Christmas holiday, our kitchen has fed more people than normal and cleaning has therefore increased.  I have been giving a lot of thought to the possible benefits and risks of using antimicrobial cleaners and soaps.  When you get into this subject, you find it is actually quite complex.

I have written about something similar before, but there is now a lot of published work that suggests that in most cases, there is no benefit to using antibacterial soaps in the home - there is no statistically significant reduction in infectious disease if antibacterial preparations are used in preference to soap and water*.  Nevertheless, in the US alone, nearly $1 billion per year is spent on antibacterial soaps**.

Of course, many infectious diseases are caused by viruses; they are probably not affected by antibacterial compounds, which have a definite target in the bacterial cell.  Thus, an antibacterial soap or wipe will be no better at preventing transmission of cold viruses than a thorough cleaning with soap or detergent and water.

I have recently been asked to review a couple of scientific papers in which evidence is presented that suggests cleaning agents commonly used in the food industry may induce antibiotic resistance in bacteria.  Antibiotic resistance results when bacteria develop enzymes capable of breaking down the active component of the antibiotic.  One of the first instances of antibiotic resistance occurred very soon after the introduction of penicillin.  Bacteria developed the ability to break the beta-lactam ring of penicillin with an enzyme called beta-lactamase.  (Antibiotic resistance genes can often be transferred from one bacterium to another, so in time, many bacterial strains become resistant.)

We already know that many of our antibiotics are no longer effective because of resistance.  Overuse of antibiotics is blamed.  It is ironic that our cleaning agents may also be causing resistance.

But there is another potential driver for antibiotic resistance: sub-lethal exposure of bacteria to certain herbicides have been shown to change antibiotic susceptibility of Escherichia coli and Salmonella enterica serovar Typhimurium***.  This is not a straightforward relationship, but it is clear that there is the potential to select for antibiotic resistance in these bacteria, which, if transferred to humans by contact with animals and food, can potentially reduce the effectiveness of antibiotic therapy.

Well, that's fairly heavy for the first post of 2016, but it should cause us to think when purchasing home cleaning agents and soaps, or chemicals for use in agriculture and domestic gardens.

* Effect of Antibacterial Home Cleaning and Handwashing Products on Infectious Disease Symptoms.  Larson, Elaine L;Lin, Susan X;Gomez-Pichardo, Cabilia;Della-Latta, Phyllis.  Annals of Internal Medicine; Mar 2, 2004; 140, 5


*** Kurenbach B, Marjoshi D, Amábile-Cuevas CF, Ferguson GC, Godsoe W, Gibson P, Heinemann JA. 2015. Sublethal exposure to commercial formulations of the herbicides dicamba, 2,4-dichlorophenoxyacetic acid, and glyphosate cause changes in antibiotic susceptibility in Escherichia coli and Salmonella enterica serovar Typhimurium.  
mBio 6(2):e00009-15. doi:10.1128/mBio.00009-15.

Saturday, January 2, 2016

Lies, damned lies, and misinterpretation of the data.

I am constantly amazed by the apparent ignorance and credulity of the general public on matters of food safety and nutrition.  But should I be surprised?   Few people are lucky enough to have studied food technology, food science or nutrition.  Their main sources of information are then the popular press, magazines, television cooking shows and the all-pervasive Internet. 

Scientists and engineers know that the best sources of information are peer-reviewed papers published in international journals.  Experts in the field have read the paper and picked it apart, looking for poor experimental design, inconsistencies and faulty interpretation of data.  Believe me, I can say this with certainty from both sides of the fence: it is pretty difficult to get a paper published these days!

The other sources of information mentioned above are generally not peer-reviewed.  Articles can be published by people with no formal qualifications in the subject and are often either highly biased or downright wrong.  See:

Sensationalism and sycophantic following of media celebrities are what sell newspapers and magazines.  We see more food scares and wonder diet advice every month without any reference to the original research.

A few examples spring to mind:

Towards the end of October 2015, the WHO International Agency for Research on Cancer stated that processed meats, including hot dogs and sausages would be added to its list of high risk carcinogens.  Red meats were also declared a probable carcinogen.  Needless to say, this caused a furore in all the media.  A Google search, using the terms “sausages cause cancer” returned 469,000 results!  IARC classifications rank the quality of the evidence that something can cause cancer, but don’t assess the level of risk. The announcement was often quoted out of context.  For example, Discovery News baldly stated “Eating sausages, ham and other processed meats causes colon cancer”.  Other reports mentioned the increase in risk as a percentage, but did not state the base level of risk. This scare is enduring; at a barbecue recently, someone noted that I was cooking “cancer sticks”.

Coconut water appears to have been a major drink commodity this year. I have no sales figures, but the sales in 2013 were around half a billion dollars, see  Claims for coconut water include helping with weight loss, improving skin tone and aiding digestion.   Other claims, now withdrawn, stated that it could fight kidney disease, osteoporosis and viruses.  Coconut water contains potassium, calcium, magnesium and phosphorus, which are required minerals.  As a sports rehydration drink, coconut water is definitely unsuitable - when we sweat, we lose lots of sodium.  The ratio of sodium to potassium in sweat is about 10:1, but the ratio of sodium to potassium in coconut water is around 1:3.  Where are the peer reviewed scientific studies of the value of coconut water? They are never quoted.

Critics of the hypothesis that saturated fat consumption is linked with coronary heart disease use the argument that the correlation between total saturated fatty acids and risk factors is not very good.  Unfortunately, the scientific findings have been misinterpretated by the popular press media, with the result that we are told we can eat as much saturated fat as we wish. This advice is incorrect, unethical and irresponsible, see

Despite all the information on food safety available, in my opinion, a large proportion of the population is still badly educated in this regard.  At an outdoor party this week (it's summer in New Zealand) I sat with a very-soon-to-be mother.  She got stuck into the soft cheese in a big way, but said that she would eat it only during the first half hour of its being unwrapped; thereafter it was to be avoided.  In fact, the cheese had been made with pasteurised milk and she was therefore probably safe in eating it, but where had she got this idea from?  I guess she had read about Listeria in soft cheeses, and believed that the bacteria could multiply as the cheese warmed up.  For reliable information on safe foods to eat during pregnancy, see:

I believe that food scientists and food technologists have a duty to provide unbiased and easily digested (sorry!) information to the public in order to help educate them in food safety.  But how can we compete with big advertising budgets and the pronouncements of media celebrities?

I wish all my readers a happy, successful and safe 2016.