Last week I retired from AUT, ending my career of 36 years in New Zealand as a food microbiologist and several years before that in the UK and Australia as a biochemical engineer. The AUT e-mail address will probably operate for some months, but the header to this blog shows my other contact address: FoodMicrobiologist.007@gmail.com
I will continue to write this blog when interesting food safety issues arise, or when someone poses a question that triggers new thoughts.
I wish all my readers a happy and safe Christmas holiday.
Saturday, December 21, 2013
Thursday, November 14, 2013
The two/five/ten second rule
I was contacted today by a TV presenter who wanted me to comment on the supposed rule that says "If you drop food on the floor, it's OK to eat it if you pick it up before two, five or ten seconds". The length of time depends on who tells you the rule.
THERE IS NO RULE!
Think of the possible permutations: you drop a chocolate on your clean carpet; you drop a lettuce leaf on your clean kitchen floor and perhaps rinse it under the tap; you always take your shoes off when you enter the house and you drop a sandwich on the clean carpet; you are out at the races and your kid drops his hotdog on the grass.
These situations are very different, but they all have one thing in common: the floor, carpet and grass are all places where people tread and possibly where animals tread too. Even in your clean house, there may be pets that shed hair and you have no idea which part of their anatomy is shedding.
If it's OK to do it at home, would you be happy to see food dropped on the floor in a restaurant picked up and put back on a plate?
I guess ultimately, it's a matter of personal opinion, at least in the domestic situation, but we know that microorganisms can transfer from one surface to another with amazing rapidity. The chances of getting an infecting dose of pathogens from eating food that has momentarily been on the floor is small, but is it worth the risk? What else is on the floor?
The difficulty, of course, is that you wouldn't give a baby food that has been dropped on the floor, but as soon as the baby starts to crawl, it will put anything in its mouth and thereby starts to build up immunity to bacteria in its environment. How do you decide?
For what it's worth, my professional opinion is that no food should be consumed if it has been on the floor.
THERE IS NO RULE!
Think of the possible permutations: you drop a chocolate on your clean carpet; you drop a lettuce leaf on your clean kitchen floor and perhaps rinse it under the tap; you always take your shoes off when you enter the house and you drop a sandwich on the clean carpet; you are out at the races and your kid drops his hotdog on the grass.
These situations are very different, but they all have one thing in common: the floor, carpet and grass are all places where people tread and possibly where animals tread too. Even in your clean house, there may be pets that shed hair and you have no idea which part of their anatomy is shedding.
If it's OK to do it at home, would you be happy to see food dropped on the floor in a restaurant picked up and put back on a plate?
I guess ultimately, it's a matter of personal opinion, at least in the domestic situation, but we know that microorganisms can transfer from one surface to another with amazing rapidity. The chances of getting an infecting dose of pathogens from eating food that has momentarily been on the floor is small, but is it worth the risk? What else is on the floor?
The difficulty, of course, is that you wouldn't give a baby food that has been dropped on the floor, but as soon as the baby starts to crawl, it will put anything in its mouth and thereby starts to build up immunity to bacteria in its environment. How do you decide?
For what it's worth, my professional opinion is that no food should be consumed if it has been on the floor.
I don't know where this image originated; I found it on the Internet.
Thursday, August 29, 2013
Clostridium botulinum vs Clostridium sporogenes
Over the last couple of weeks, I have been interviewed many times by radio, television and newspaper reporters on the issue of the Fonterra whey protein concentrate scare and the resulting recall of infant feeding formulae.
One question that has always cropped up is "Why did it take so long for the company and Ministry of Primary Industry to tell the public whether the contaminant was Clostridium botulinum or Clostridium sporogenes?"
I have never knowingly worked with C. botulinum. It's a dangerous organism because it produces a neurotoxin and special precautions are necessary to work with it. But when working with food samples and isolating anaerobes (microorganisms that grow in the absence of oxygen), there is always the possibility of unwittingly isolating and amplifying something dangerous.
However, some of my associates have worked with these bacteria. They tell me that the two bacteria are very difficult to distinguish. Indeed, Dr Heather Hendrickson, lecturer in evolutionary genetics, Massey University, has said that the two bacteria differ by only one gene. So obviously, growing the bacteria in culture media and conducting biochemical testing will not allow them to be distinguished. Very specific molecular techniques must be applied to show the difference and I am told that there are difficulties in carrying out this method. ESR in New Zealand has the ability to conduct these analyses.
Just for interest, I searched for SEM images of the two bacteria and found the following on-line. Both images are false colour, and show the impossibility of telling them apart by their appearance. See the difference?
One question that has always cropped up is "Why did it take so long for the company and Ministry of Primary Industry to tell the public whether the contaminant was Clostridium botulinum or Clostridium sporogenes?"
I have never knowingly worked with C. botulinum. It's a dangerous organism because it produces a neurotoxin and special precautions are necessary to work with it. But when working with food samples and isolating anaerobes (microorganisms that grow in the absence of oxygen), there is always the possibility of unwittingly isolating and amplifying something dangerous.
However, some of my associates have worked with these bacteria. They tell me that the two bacteria are very difficult to distinguish. Indeed, Dr Heather Hendrickson, lecturer in evolutionary genetics, Massey University, has said that the two bacteria differ by only one gene. So obviously, growing the bacteria in culture media and conducting biochemical testing will not allow them to be distinguished. Very specific molecular techniques must be applied to show the difference and I am told that there are difficulties in carrying out this method. ESR in New Zealand has the ability to conduct these analyses.
Just for interest, I searched for SEM images of the two bacteria and found the following on-line. Both images are false colour, and show the impossibility of telling them apart by their appearance. See the difference?
Wednesday, August 28, 2013
Clostridium in whey protein turns out not to be C. botulinum
The Ministry of Primary Industry today made a statement that tests on the Clostridium species isolated from Fonterra whey protein concentrate show that it is not C. botulinum. The organism is C. sporogenes and poses no food poisoning threat.
This will be a huge relief to Fonterra, the New Zealand government and MPI, not to mention hundreds of parents of babies being fed on infant formula. However, the damage to the company's reputation and the Pure New Zealand brand has been massive. Even countries that did not receive any of the affected powder and formulae have banned the import of New Zealand dairy products.
Why has it taken so long to get a definitive answer and why did the company recall the product?
Tests of products that incorporated certain batches of whey protein concentrate showed growth of sulphite reducing clostridia, though the protein concentrate itself was within specification. Further testing of the bacterial isolates suggested that they might be C. botulinum. Because of the severity of the illness that this microorganism can cause, the company withdrew certain batches of whey protein concentrate from the market and advised its customers accordingly.
It is quite difficult to distinguish certain closely related types of bacteria, and this is the case with C. botulinum and C. sporogenes. The bacteria have to be isolated in pure culture, various biochemical tests must be performed, DNA must be extracted and PCR reactions carried out with specific primers. While this sounds easy, and appears to be very rapid if the CSI-type of TV programmes are to be believed, in practice it is very tricky and time consuming. Extracting the DNA from the bacteria without its being degraded by DNAse enzymes is apparently difficult. There are few laboratories in the world capable of carrying out the testing reliably. (This is not a bacterium to be trifled with. When I worked in England for a year at the Food Research Institute in Norwich, only vaccinated people were permitted to go into the botulinum laboratory because of the risk to workers of lethal intoxication). The 'gold standard' test for toxigenic C. botulinum capable of causing the neuroparalysis is the mouse lethality test. This must be performed very precisely, according to an internationally recognised approved procedure and involves specially bred mice of a particular age. The various tests have now been completed, allowing the announcement from MPI today.
Did Fonterra do the right thing in notifying its customers of the potentially hazardous product and recalling the protein concentrate? In my opinion, they did. Certainly, it has caused the company embarrassment and financial loss, but what of the other option - keeping quiet and hoping the problem would go away? The death of even a single baby from botulism would have been far more damaging, and devastating for the parents.
Will things change in the future? Only time will tell what regulatory changes may follow, and new testing requirements are imposed. One thing is sure: occasionally, food manufacturers will make a mistake; equipment will malfunction, or a set of circumstances will come together that result in potentially unsafe food. The entire food industry must strive to reduce the frequency of these incidents to an absolute minimum by close process control, based on appropriate and robust risk assessment and hazard control measures.
This will be a huge relief to Fonterra, the New Zealand government and MPI, not to mention hundreds of parents of babies being fed on infant formula. However, the damage to the company's reputation and the Pure New Zealand brand has been massive. Even countries that did not receive any of the affected powder and formulae have banned the import of New Zealand dairy products.
Why has it taken so long to get a definitive answer and why did the company recall the product?
Tests of products that incorporated certain batches of whey protein concentrate showed growth of sulphite reducing clostridia, though the protein concentrate itself was within specification. Further testing of the bacterial isolates suggested that they might be C. botulinum. Because of the severity of the illness that this microorganism can cause, the company withdrew certain batches of whey protein concentrate from the market and advised its customers accordingly.
It is quite difficult to distinguish certain closely related types of bacteria, and this is the case with C. botulinum and C. sporogenes. The bacteria have to be isolated in pure culture, various biochemical tests must be performed, DNA must be extracted and PCR reactions carried out with specific primers. While this sounds easy, and appears to be very rapid if the CSI-type of TV programmes are to be believed, in practice it is very tricky and time consuming. Extracting the DNA from the bacteria without its being degraded by DNAse enzymes is apparently difficult. There are few laboratories in the world capable of carrying out the testing reliably. (This is not a bacterium to be trifled with. When I worked in England for a year at the Food Research Institute in Norwich, only vaccinated people were permitted to go into the botulinum laboratory because of the risk to workers of lethal intoxication). The 'gold standard' test for toxigenic C. botulinum capable of causing the neuroparalysis is the mouse lethality test. This must be performed very precisely, according to an internationally recognised approved procedure and involves specially bred mice of a particular age. The various tests have now been completed, allowing the announcement from MPI today.
Did Fonterra do the right thing in notifying its customers of the potentially hazardous product and recalling the protein concentrate? In my opinion, they did. Certainly, it has caused the company embarrassment and financial loss, but what of the other option - keeping quiet and hoping the problem would go away? The death of even a single baby from botulism would have been far more damaging, and devastating for the parents.
Will things change in the future? Only time will tell what regulatory changes may follow, and new testing requirements are imposed. One thing is sure: occasionally, food manufacturers will make a mistake; equipment will malfunction, or a set of circumstances will come together that result in potentially unsafe food. The entire food industry must strive to reduce the frequency of these incidents to an absolute minimum by close process control, based on appropriate and robust risk assessment and hazard control measures.
Friday, August 9, 2013
What is "sporulation"?
A friend asked me today "What is sporulation?"
There are essentially two genera of bacteria - Clostridium and Bacillus - that can produce very resistant stages called "spores" in response to unfavourable environmental conditions. In contrast to the vegetative, or growing, cells, the spores are resistant to many environmental conditions, including heating and drying. While the vegetative cells may be killed by heating to about 75C, the spores of C. botulinum can withstand boiling for more than four hours.
History gives us an example of how resistant spores can be:
In 1946, the British undertook some biological warfare experiments on Gruinard Island in the Inner Hebrides. Small bombs containing anthrax spores (from Bacillus anthracis) were detonated near to groups of tethered sheep. Within days, the animals were dying. The government realised that the island would be hazardous to all mammals and quarantined the island indefinitely, occasionally testing the soil for viable anthrax spores. On every testing occasion, the spores were shown to be viable. This continued until a public campaign in 1981 forced the decontamination of the island. This was achieved in 1986 by spraying 280 tonnes of formaldehyde solution onto the island and removing the most heavily contaminated topsoil. The island was demonstrated to be safe and returned to its original owners.
It's important to note that soil normally contains some bacterial spores, including those of C. botulinum. That means that raw vegetables and fruit carrying soil will often also be carrying spores. Even milk drawn from healthy cows may initially be contaminated with soil organisms from their hides. The normal pasteurisation process will kill the vegetative cells, but not the spores.
There are essentially two genera of bacteria - Clostridium and Bacillus - that can produce very resistant stages called "spores" in response to unfavourable environmental conditions. In contrast to the vegetative, or growing, cells, the spores are resistant to many environmental conditions, including heating and drying. While the vegetative cells may be killed by heating to about 75C, the spores of C. botulinum can withstand boiling for more than four hours.
History gives us an example of how resistant spores can be:
In 1946, the British undertook some biological warfare experiments on Gruinard Island in the Inner Hebrides. Small bombs containing anthrax spores (from Bacillus anthracis) were detonated near to groups of tethered sheep. Within days, the animals were dying. The government realised that the island would be hazardous to all mammals and quarantined the island indefinitely, occasionally testing the soil for viable anthrax spores. On every testing occasion, the spores were shown to be viable. This continued until a public campaign in 1981 forced the decontamination of the island. This was achieved in 1986 by spraying 280 tonnes of formaldehyde solution onto the island and removing the most heavily contaminated topsoil. The island was demonstrated to be safe and returned to its original owners.
It's important to note that soil normally contains some bacterial spores, including those of C. botulinum. That means that raw vegetables and fruit carrying soil will often also be carrying spores. Even milk drawn from healthy cows may initially be contaminated with soil organisms from their hides. The normal pasteurisation process will kill the vegetative cells, but not the spores.
Saturday, August 3, 2013
Clostridium botulinum causes problems for Fonterra
Fonterra, New Zealand's largest dairy manufacturer, last week issued a warning that Clostridium botulinum had been found in three batches of whey protein, (approximately 40 tonnes), which can be used to boost the protein content of many foods, including infant feeding formula.
The warning caused a New Zealand manufacturer of infant feeding formula to recall certain batches of product. Fonterra Chief Executive, Theo Spierings also flew to China to discuss the issue with Chinese food safety authorities.
Apparently, the source of the bacteria has been traced to a dirty pipe in a processing factory. If this is true, it's a serious lapse in process control and obviously should not have occurred.
The whey was made in May 2012 and it is unclear why the contamination has taken so long to come to light and why the company has been so slow to inform the government and the public. The company became aware of the contamination in March, but it was not until Wednesday 31st July 2013 that tests confirmed the presence of the bacteria.
There are some possible explanations for the delay: third parties may have tested the product at some point in their own manufacturing operations and found it; the contamination levels may be very low, resulting in a requirement to test large amounts of product before the contaminants were found. Certainly, once the bacteria had been isolated, using modern methods,it should not have taken long to confirm the identification.
It is not usual to test dairy products for the presence of Clostridium botulinum. When bacteria occur in a product at very low level and very infrequently, testing is ineffective in assuring safety and the cost is prohibitive. An Australian specification for whey protein concentrate does not mention Clostridia.
The concern about the presence of C. botulinum is real and justified. The bacteria can produce a potent neurotoxin that causes paralysis and death. There have been only a couple of cases in New Zealand in the last 35 years. The toxin is released when the cells sporulate, so growth of the bacteria is necessary for toxin production. Bacteria cannot grow at the low water activity conditions in whey protein powder, but spores could germinate and grow if infant formula containing the contaminated whey protein were made up and then held warm for some period. The other very serious scenario is that infants fed the contaminated formula might then suffer botulism when the spores grow in the intestinal tract.
This story is not over yet and Safe Food will monitor the developments.
The warning caused a New Zealand manufacturer of infant feeding formula to recall certain batches of product. Fonterra Chief Executive, Theo Spierings also flew to China to discuss the issue with Chinese food safety authorities.
Apparently, the source of the bacteria has been traced to a dirty pipe in a processing factory. If this is true, it's a serious lapse in process control and obviously should not have occurred.
The whey was made in May 2012 and it is unclear why the contamination has taken so long to come to light and why the company has been so slow to inform the government and the public. The company became aware of the contamination in March, but it was not until Wednesday 31st July 2013 that tests confirmed the presence of the bacteria.
There are some possible explanations for the delay: third parties may have tested the product at some point in their own manufacturing operations and found it; the contamination levels may be very low, resulting in a requirement to test large amounts of product before the contaminants were found. Certainly, once the bacteria had been isolated, using modern methods,it should not have taken long to confirm the identification.
It is not usual to test dairy products for the presence of Clostridium botulinum. When bacteria occur in a product at very low level and very infrequently, testing is ineffective in assuring safety and the cost is prohibitive. An Australian specification for whey protein concentrate does not mention Clostridia.
The concern about the presence of C. botulinum is real and justified. The bacteria can produce a potent neurotoxin that causes paralysis and death. There have been only a couple of cases in New Zealand in the last 35 years. The toxin is released when the cells sporulate, so growth of the bacteria is necessary for toxin production. Bacteria cannot grow at the low water activity conditions in whey protein powder, but spores could germinate and grow if infant formula containing the contaminated whey protein were made up and then held warm for some period. The other very serious scenario is that infants fed the contaminated formula might then suffer botulism when the spores grow in the intestinal tract.
This story is not over yet and Safe Food will monitor the developments.
Saturday, July 27, 2013
Raw milk linked with food poisoning in New Zealand
I have written several times about the hazards of drinking raw milk (see the label "raw milk"). Using Ministry of Health information obtained under the Official Information Act, Talia Shadwell has written about food poisoning linked with consumption of raw milk in the Manawatu and Waikato, two regions of New Zealand.
A total of nine people, including two young children, were hospitalised in March, suffering from Escherichia coli infection. A month later, six people contracted campylobacteriosis. A common factor in all these cases was apparently consumption of raw milk.
What is of great concern to me is that these patients revealed that they had little knowledge of the hazards of drinking raw milk, despite the publicity given to such outbreaks.
I would uphold the right of individuals to consume raw foods if they so wish, but they should be fully aware of the risks and remember that their children do not really have the luxury of food choice.
A total of nine people, including two young children, were hospitalised in March, suffering from Escherichia coli infection. A month later, six people contracted campylobacteriosis. A common factor in all these cases was apparently consumption of raw milk.
What is of great concern to me is that these patients revealed that they had little knowledge of the hazards of drinking raw milk, despite the publicity given to such outbreaks.
I would uphold the right of individuals to consume raw foods if they so wish, but they should be fully aware of the risks and remember that their children do not really have the luxury of food choice.
Tuesday, July 16, 2013
Talking crap
Microbiologists,
and particularly food microbiologists, are rarely invited to be
after-dinner speakers - our interests are just too awful!
I recently listened to a TED talk that set me thinking. This blog is about safe food and, I admit, tends to concentrate on microorganisms in food. Safe food should be the right of every man, woman and child on earth; without it, life becomes unpleasant, and in some cases, unsafe food can be the cause of death.
We read about the devastation that can be caused by HIV, but apparently, the major cause of infant death is diarrhoea. The latter is easy to treat, but without clean water and good sanitation, many children die. My daughter-in-law recently presented me with a granddaughter. It's a long time since I held a new-born baby, but I realised just how tiny a new-born is - they can't afford to lose large amounts of fluid.
As the TED lecturer said, we take clean water and flush toilets for granted, but a large proportion of the world's population don't have even suitable latrines.
Have a look
at an attractive woman talking crap:
http://video.ted.com/talk/ podcast/2013/None/ RoseGeorge_2013.mp4
Tuesday, June 4, 2013
Third World water supply
Residents of this village have been boiling their water for drinking for the past four years. They have just been told that they can expect to do this for at least another ten years, because upgrading the supply is not a priority.
The village water supply, which is drawn from an open stream, was described by the regional mayor as "Potentially safe to drink, most of the time". There is the possibility of Giardia and Cryptosporidium contamination in the water supply. Doesn't sound too good does it?
The UN General Assembly declared on 28th July 2010 that safe and clean drinking water and sanitation is a human right essential to the full enjoyment of life and all other human rights. The General Assembly also voiced deep concern that almost 900 million people worldwide do not have access to clean water.
So, is this village in Africa, South America, or India? No. It's in the North Island of New Zealand. That puts these residents on a par with many Third World countries.
Mathew Grocot, writing in the Manawatu Standard this week, reports that the Horowhenua District Mayor told the local residents association that the minimum period before residents could expect to see a tangible improvement in their water supply was ten years. Water and sewage projects in the district would cost more than $100 million over the next 20 years. Another town in the district had priority for upgrade of its water and sewage systems.
Some residents were predictably annoyed when told that other infrastructure projects, including a community centre, library and park upgrades in other towns had priority. When asked why these projects were deemed more important than the village water supply, the mayor said that if these community facilities were not provided, people would not want to live in the district.
Seems to me that crap in the water is a really good reason not to live there.
The village water supply, which is drawn from an open stream, was described by the regional mayor as "Potentially safe to drink, most of the time". There is the possibility of Giardia and Cryptosporidium contamination in the water supply. Doesn't sound too good does it?
The UN General Assembly declared on 28th July 2010 that safe and clean drinking water and sanitation is a human right essential to the full enjoyment of life and all other human rights. The General Assembly also voiced deep concern that almost 900 million people worldwide do not have access to clean water.
So, is this village in Africa, South America, or India? No. It's in the North Island of New Zealand. That puts these residents on a par with many Third World countries.
Mathew Grocot, writing in the Manawatu Standard this week, reports that the Horowhenua District Mayor told the local residents association that the minimum period before residents could expect to see a tangible improvement in their water supply was ten years. Water and sewage projects in the district would cost more than $100 million over the next 20 years. Another town in the district had priority for upgrade of its water and sewage systems.
Some residents were predictably annoyed when told that other infrastructure projects, including a community centre, library and park upgrades in other towns had priority. When asked why these projects were deemed more important than the village water supply, the mayor said that if these community facilities were not provided, people would not want to live in the district.
Seems to me that crap in the water is a really good reason not to live there.
Saturday, May 25, 2013
European food regulators make asses of themselves again.
Of course, it would be illegal to pass off one sort of meat as another, but this post is not about false labelling.
This time, the European Union wanted to ban olive oil jugs and dipping bowls from restaurant tables, replacing these traditional offerings with sealed, pre-packaged containers of oil.
See:
http://www.telegraph.co.uk/news/worldnews/europe/eu/10064787/EU-to-ban-olive-oil-jugs-from-restaurants.html
Not surprisingly, this has caused some negative comment from restaurateurs, producers, food writers and some politicians, including the British Prime Minister, who made a painful word play, saying that this measure "Shouldn't even be on the table".
Apparently, the EU now says that the measure will be rescinded, but I suspect we have not heard the end of it, as major olive oil producers, including Italy, Greece, Spain and Portugal, supported the measure, and farmer lobby groups have vowed to fight on.
See:
http://www.nytimes.com/2013/05/24/world/europe/european-commission-tables-olive-oil-rule.html?partner=rss&emc=rss&_r=1&
Odd spot: if you want to read some more of the EU shenanigans, have a look at the definition of 'strawberry'. I've read that bananas, cucumbers and Cornish Pasties have also had a troubled time in the regulations.
This time, the European Union wanted to ban olive oil jugs and dipping bowls from restaurant tables, replacing these traditional offerings with sealed, pre-packaged containers of oil.
See:
http://www.telegraph.co.uk/news/worldnews/europe/eu/10064787/EU-to-ban-olive-oil-jugs-from-restaurants.html
Not surprisingly, this has caused some negative comment from restaurateurs, producers, food writers and some politicians, including the British Prime Minister, who made a painful word play, saying that this measure "Shouldn't even be on the table".
Apparently, the EU now says that the measure will be rescinded, but I suspect we have not heard the end of it, as major olive oil producers, including Italy, Greece, Spain and Portugal, supported the measure, and farmer lobby groups have vowed to fight on.
See:
http://www.nytimes.com/2013/05/24/world/europe/european-commission-tables-olive-oil-rule.html?partner=rss&emc=rss&_r=1&
Odd spot: if you want to read some more of the EU shenanigans, have a look at the definition of 'strawberry'. I've read that bananas, cucumbers and Cornish Pasties have also had a troubled time in the regulations.
Sunday, May 12, 2013
TV chefs fail at basic hand hygiene
I have just watched famous TV chefs preparing demonstration dishes. One worked in his kitchen, others in an outside setting.
In both cases, the chefs were handling raw meat with their bare hands and preparing salads and sauces. At no point did the chefs wash their hands and of course, they were moving between raw meats, fresh vegetables and spices.
Of most concern to me was the use of a towel. Chefs often have a towel at their waist; they use it for wiping spills from plates prior to service. On this occasion, the chef handled the raw meat and repeatedly wiped his hands on the towel. The sauce was blended from fresh vegetables and was not cooked. There were no hand washing facilities in the shot and the sauce vegetables were also handled with bare hands. The potential for food poisoning is significant.
Now, perhaps the chefs really did wash their hands between handling raw meats and salads. However, these are demonstrations for ordinary viewers. They should be setting a better example and emphasising the necessity of hand washing.
In both cases, the chefs were handling raw meat with their bare hands and preparing salads and sauces. At no point did the chefs wash their hands and of course, they were moving between raw meats, fresh vegetables and spices.
Of most concern to me was the use of a towel. Chefs often have a towel at their waist; they use it for wiping spills from plates prior to service. On this occasion, the chef handled the raw meat and repeatedly wiped his hands on the towel. The sauce was blended from fresh vegetables and was not cooked. There were no hand washing facilities in the shot and the sauce vegetables were also handled with bare hands. The potential for food poisoning is significant.
Now, perhaps the chefs really did wash their hands between handling raw meats and salads. However, these are demonstrations for ordinary viewers. They should be setting a better example and emphasising the necessity of hand washing.
Labels:
food handling,
food poisoning,
Hand washing,
kitchen hygiene,
TV chef
Tuesday, May 7, 2013
Food Fraud
Food fraud is nothing new - it was mentioned in the UK in 1771 by Thomas Smollet and food adulteration was common in the Victorian era.
Food fraud usually takes the form of passing off inferior materials as more expensive products. It can be as simple as adding chalk to flour, supplementation of milk powder with melamine or passing off a low value product as one of greater worth. The latter often involves violation of trade marks or brand names.
Why do unscrupulous suppliers do this? Simply put, it's greed. If you can sell low value materials as high quality products, you can make a killing. Sometimes this occurs literally, for example, the not uncommon adulteration of spirits with methanol, an industrial chemical, or the attempt to smooth wine by adding glycol.
When I first began teaching in a Bachelor of Food Technology degree, I was horrified to read a full-page advertisement in a glossy trade magazine: "Why sell meat when you can sell water?" The advertiser was selling sodium tripolyphosphate, a water binding agent that can be injected into meats including fish. It makes the meat appear more succulent and acts as a preservative, but also increases the sale weight.
So this practice continues. The most recent description comes from foodprocessing.com.au
It appears that the authorities in China have been investigating many cases of food fraud and over 900 people have been arrested. One example is the manufacture of fake mutton from fox, mink and rat by the addition of chemicals. The amounts involved are truly staggering (where do they find so many foxes?). Presumably, the meat is comminuted, as cuts of rat are unlikely to be similar to mutton, though it might be a different matter with fox meat. It would be particularly disturbing if the products were labelled "Product of New Zealand" - this is a prime example of "passing off". It would not be the first time this sort of thing has happened.
Food fraud in any form is stealing. The consumer is not getting what he or she is paying for. The Chinese authorities are right to come down hard on the perpetrators, but it's an extremely difficult thing to stamp out because of the enormous rewards of getting away with it.
Food fraud usually takes the form of passing off inferior materials as more expensive products. It can be as simple as adding chalk to flour, supplementation of milk powder with melamine or passing off a low value product as one of greater worth. The latter often involves violation of trade marks or brand names.
Why do unscrupulous suppliers do this? Simply put, it's greed. If you can sell low value materials as high quality products, you can make a killing. Sometimes this occurs literally, for example, the not uncommon adulteration of spirits with methanol, an industrial chemical, or the attempt to smooth wine by adding glycol.
When I first began teaching in a Bachelor of Food Technology degree, I was horrified to read a full-page advertisement in a glossy trade magazine: "Why sell meat when you can sell water?" The advertiser was selling sodium tripolyphosphate, a water binding agent that can be injected into meats including fish. It makes the meat appear more succulent and acts as a preservative, but also increases the sale weight.
So this practice continues. The most recent description comes from foodprocessing.com.au
It appears that the authorities in China have been investigating many cases of food fraud and over 900 people have been arrested. One example is the manufacture of fake mutton from fox, mink and rat by the addition of chemicals. The amounts involved are truly staggering (where do they find so many foxes?). Presumably, the meat is comminuted, as cuts of rat are unlikely to be similar to mutton, though it might be a different matter with fox meat. It would be particularly disturbing if the products were labelled "Product of New Zealand" - this is a prime example of "passing off". It would not be the first time this sort of thing has happened.
Food fraud in any form is stealing. The consumer is not getting what he or she is paying for. The Chinese authorities are right to come down hard on the perpetrators, but it's an extremely difficult thing to stamp out because of the enormous rewards of getting away with it.
Monday, May 6, 2013
Veggies that glow in the dark?
You must have heard the old joke that one advantage of irradiated food is that you can find it during a power outage.
Unfortunately, this sort of misunderstanding about food irradiation is common. The food doesn't become radioactive and it doesn't glow in the dark. Appropriate use of irradiation can prevent sprouting in potatoes or can be used for disinfestation.
The subject has come to prominence again with the stated intention of the New Zealand government to permit the import from Australia of irradiated tomatoes and peppers.
Exposure of vegetables to low levels of ionising radiation kills insects, rendering the vegetables safe for importation to New Zealand without the need to use chemicals such as methyl bromide**. New Zealand agriculture could be severely affected if certain insect pests were able to enter and establish in the country.
What effect could this irradiation have on the nutritional quality of the food and the health of consumers? There are some very minor changes in the food - levels of the vitamin thiamine are slightly reduced, but not sufficiently to result in thiamine deficiency (and there are other sources of thiamine besides imported tomatoes and peppers). Indeed, the changes in food are so minor as to make it difficult to determine whether food has been irradiated or not.
Opponents of irradiation claim that the minor changes that occur in the food show that the process should not be permitted. However, they neglect the changes induced by other processing methods. Who could argue that a canned peach is the same as a fresh one? In fact, careful study shows that all the chemical changes produced by irradiation can also be detected when foods are processed by more conventional means.
Other arguments are that unscrupulous food manufacturers will use irradiation to defraud the consumer by covering up spoilage. This is plain nonsense. If spoiled bacon, for example, were irradiated at sufficiently high dosage, microbiological testing would give low or zero microbial counts. But the bacon would still be spoiled and a taste test would show this.
Irradiation is the most extensively studied form of food preservation, and the weight of expert opinion is that irradiated foods are safe for human consumption.
A number of years ago, a European supermarket put irradiated foods on the shelves alongside similar foods not treated. The irradiated foods were labelled, so that there was no attempt to deceive the consumers. However, consumers appeared to select the irradiated foods in preference for the non-irradiated.
The issue is not about safety, but about consumer perception.
** Methyl bromide was formerly used extensively in many countries to disinfest a wide range of agricultural materials in many countries. Unfortunately, it is also an ozone-depleting compound and was phased out in most countries between 1995 and 2005.
Unfortunately, this sort of misunderstanding about food irradiation is common. The food doesn't become radioactive and it doesn't glow in the dark. Appropriate use of irradiation can prevent sprouting in potatoes or can be used for disinfestation.
The subject has come to prominence again with the stated intention of the New Zealand government to permit the import from Australia of irradiated tomatoes and peppers.
Exposure of vegetables to low levels of ionising radiation kills insects, rendering the vegetables safe for importation to New Zealand without the need to use chemicals such as methyl bromide**. New Zealand agriculture could be severely affected if certain insect pests were able to enter and establish in the country.
What effect could this irradiation have on the nutritional quality of the food and the health of consumers? There are some very minor changes in the food - levels of the vitamin thiamine are slightly reduced, but not sufficiently to result in thiamine deficiency (and there are other sources of thiamine besides imported tomatoes and peppers). Indeed, the changes in food are so minor as to make it difficult to determine whether food has been irradiated or not.
Opponents of irradiation claim that the minor changes that occur in the food show that the process should not be permitted. However, they neglect the changes induced by other processing methods. Who could argue that a canned peach is the same as a fresh one? In fact, careful study shows that all the chemical changes produced by irradiation can also be detected when foods are processed by more conventional means.
Other arguments are that unscrupulous food manufacturers will use irradiation to defraud the consumer by covering up spoilage. This is plain nonsense. If spoiled bacon, for example, were irradiated at sufficiently high dosage, microbiological testing would give low or zero microbial counts. But the bacon would still be spoiled and a taste test would show this.
Irradiation is the most extensively studied form of food preservation, and the weight of expert opinion is that irradiated foods are safe for human consumption.
A number of years ago, a European supermarket put irradiated foods on the shelves alongside similar foods not treated. The irradiated foods were labelled, so that there was no attempt to deceive the consumers. However, consumers appeared to select the irradiated foods in preference for the non-irradiated.
The issue is not about safety, but about consumer perception.
** Methyl bromide was formerly used extensively in many countries to disinfest a wide range of agricultural materials in many countries. Unfortunately, it is also an ozone-depleting compound and was phased out in most countries between 1995 and 2005.
Saturday, April 20, 2013
Safe microwaving
My wife, who has been married to a food microbiologist for 43 years, mentioned something she read in a Q & A section of a local newspaper, in which the writer discussed whether microwave heating killed Salmonella.
The main effect of putting food into a microwave oven is to cause the water molecules in the food to absorb energy. The molecules move faster and we register this as the food getting hotter. (It can be shown, by careful experiments, that there is a small effect of microwaves per se on microorganisms, but the main effect is the result of the heating).
When salmonellae and most other vegetative cells reach 75C, some critical enzymes or other cell components, such as the cell membrane, are damaged and the cells die. So the writer was correct in saying that microwave heating makes food safe.
However, there are a couple of provisos. First, it is essential that the food reaches this temperature throughout. Some microwave ovens have hot spots, so the food may appear to be boiling, but there may be areas where the temperature is much lower. This can be alleviated by stirring the food a couple of times during heating. Secondly, spores of pathogenic bacteria in the food will probably not be destroyed and may actually be activated by the heating. If the food is consumed immediately, there is no hazard, but if it is then cooled and stored, the germinating spores can multiply and may cause food poisoning. (In this regard, microwave heating is no different from stove top cooking).
Finally, when we think of food safety, we tend to think of food poisoning. However, the microwave oven can superheat liquids above boiling point. When the liquid is disturbed, perhaps by bumping the container, the superheated water can suddenly flash into steam, causing a painful burn. A couple of my students have discovered this when using a microwave oven to heat microbiological culture media.
However, in my opinion, using a microwave oven to cook or to reheat food is just as safe as a conventional stove.
The main effect of putting food into a microwave oven is to cause the water molecules in the food to absorb energy. The molecules move faster and we register this as the food getting hotter. (It can be shown, by careful experiments, that there is a small effect of microwaves per se on microorganisms, but the main effect is the result of the heating).
When salmonellae and most other vegetative cells reach 75C, some critical enzymes or other cell components, such as the cell membrane, are damaged and the cells die. So the writer was correct in saying that microwave heating makes food safe.
However, there are a couple of provisos. First, it is essential that the food reaches this temperature throughout. Some microwave ovens have hot spots, so the food may appear to be boiling, but there may be areas where the temperature is much lower. This can be alleviated by stirring the food a couple of times during heating. Secondly, spores of pathogenic bacteria in the food will probably not be destroyed and may actually be activated by the heating. If the food is consumed immediately, there is no hazard, but if it is then cooled and stored, the germinating spores can multiply and may cause food poisoning. (In this regard, microwave heating is no different from stove top cooking).
Finally, when we think of food safety, we tend to think of food poisoning. However, the microwave oven can superheat liquids above boiling point. When the liquid is disturbed, perhaps by bumping the container, the superheated water can suddenly flash into steam, causing a painful burn. A couple of my students have discovered this when using a microwave oven to heat microbiological culture media.
However, in my opinion, using a microwave oven to cook or to reheat food is just as safe as a conventional stove.
Sunday, February 10, 2013
More on horse meat scandal
I am currently in the UK and suffering from the inevitable personal clock disruption caused by long international flights, so I've been watching the BBC news, which is reporting new revelations on the horse meat scandal.
Some manufactured meat products, such as lasagna, have been found to contain not just traces of horse meat, but consisted of 100% horse meat. This is obviously not accidental and is almost certainly a deliberate intention to defraud.
Though not yet proven, it appears that the horse meat entered the French food industry via a shipment of so- called beef from an abattoir in Romania.
As I noted in a previous post, there is probably no health issue, though concern has been raised that the horses could have been treated with animal remedies that might still be present in the meat.
This story will remain in the headlines - there are calls for bans on import of meat from Europe, but this is not possible under the European single market rules. One thing is certain; the story will continue to unfold for some time.
Some manufactured meat products, such as lasagna, have been found to contain not just traces of horse meat, but consisted of 100% horse meat. This is obviously not accidental and is almost certainly a deliberate intention to defraud.
Though not yet proven, it appears that the horse meat entered the French food industry via a shipment of so- called beef from an abattoir in Romania.
As I noted in a previous post, there is probably no health issue, though concern has been raised that the horses could have been treated with animal remedies that might still be present in the meat.
This story will remain in the headlines - there are calls for bans on import of meat from Europe, but this is not possible under the European single market rules. One thing is certain; the story will continue to unfold for some time.
Monday, January 21, 2013
It's not CSI
Most of us have seen the odd episode, or at least been aware of the popular CSI-Miami or other incarnations of the crime drama TV series. Those of us who are scientists are somewhat cynical about the ease with which samples from crime scenes can be analysed, seemingly within hours, by whizzy machines in gleaming laboratories.
In most cases, this is far from the truth; analysis of DNA samples, for example, requires painstaking care during the collection and processing of the material. You only have to see the real world courtroom challenges to forensic laboratory evidence to realise that the whole process is much more complicated than the TV programmes would have us believe.
However, the detection of pathogenic bacteria in foods, or even the deliberate adulteration of beef burgers with other meats, is now benefiting from these molecular techniques.
The ability to sequence whole genomes of bacteria, coupled with the cheap synthesis of primers (probes) that will bind to specific parts of the bacterial DNA has enabled us to test for the presence of pathogenic bacteria in food samples.
In principle, we extract the bacterial DNA and add our probes to bind to unique sequences in the DNA. If the probe binds to the DNA, then we can use the Polymerase Chain Reaction** to amplify that piece of DNA and then detect it, separating it on a gel to produce a pattern of bands similar to what we see being examined on CSI. If there is no binding, no amplification occurs and no detection, so the bacteria are absent from the food.
In practice, it's a bit more complicated and time-consuming. We normally have to 'selectively enrich' our sample to increase the number of bacteria to a level at which we can detect them. We do this by adding the food to a culture medium that inhibits most other bacteria and encourages our target bacteria to grow. The actual preparation of the media, weighing the sample and putting them together takes only a couple of hours. However, we need to incubate the mixture for up to 48 hours under controlled conditions before we can run the PCR.
Over the past few weeks, I have been working with my research assistant, testing a new PCR-based method of detecting Listeria. It looks as though the method will be quicker and easier than existing methods and we'll publish our results in the near future.
Manufacturers continue to develop new rapid methods, many based on DNA and using automated equipment, making the detection of pathogens in food easier and quicker, allowing products to be checked and released to the market earlier. These methods can also be used to track down sources of contamination, such as in the European E. coli O104:H4 outbreak of 2011.
** For those readers keen to know more about PCR, I'll post a more complete description of the technique, trying to keep it relatively simple.
In most cases, this is far from the truth; analysis of DNA samples, for example, requires painstaking care during the collection and processing of the material. You only have to see the real world courtroom challenges to forensic laboratory evidence to realise that the whole process is much more complicated than the TV programmes would have us believe.
However, the detection of pathogenic bacteria in foods, or even the deliberate adulteration of beef burgers with other meats, is now benefiting from these molecular techniques.
The ability to sequence whole genomes of bacteria, coupled with the cheap synthesis of primers (probes) that will bind to specific parts of the bacterial DNA has enabled us to test for the presence of pathogenic bacteria in food samples.
In principle, we extract the bacterial DNA and add our probes to bind to unique sequences in the DNA. If the probe binds to the DNA, then we can use the Polymerase Chain Reaction** to amplify that piece of DNA and then detect it, separating it on a gel to produce a pattern of bands similar to what we see being examined on CSI. If there is no binding, no amplification occurs and no detection, so the bacteria are absent from the food.
In practice, it's a bit more complicated and time-consuming. We normally have to 'selectively enrich' our sample to increase the number of bacteria to a level at which we can detect them. We do this by adding the food to a culture medium that inhibits most other bacteria and encourages our target bacteria to grow. The actual preparation of the media, weighing the sample and putting them together takes only a couple of hours. However, we need to incubate the mixture for up to 48 hours under controlled conditions before we can run the PCR.
Over the past few weeks, I have been working with my research assistant, testing a new PCR-based method of detecting Listeria. It looks as though the method will be quicker and easier than existing methods and we'll publish our results in the near future.
Manufacturers continue to develop new rapid methods, many based on DNA and using automated equipment, making the detection of pathogens in food easier and quicker, allowing products to be checked and released to the market earlier. These methods can also be used to track down sources of contamination, such as in the European E. coli O104:H4 outbreak of 2011.
** For those readers keen to know more about PCR, I'll post a more complete description of the technique, trying to keep it relatively simple.
Wednesday, January 16, 2013
"Faster" food creates a furore
The finding of horse meat at up to 30% of a "beef" burger in Ireland has created a furore this week, both in the mainstream and social media.
The Irish Agriculture Minister, Simon Coveney, has blamed a single meat processor and has further stated that the horse meat entered the product via an imported additive, though the nature or identity of the additive was not mentioned.
You can't tell by looking at a burger just what sort of meat is present, so some fairly sophisticated laboratory methods must be used. Though not stated in the press articles I have read, the chances are that the burger was tested for specific DNA markers for horse meat. Indeed, both horse and pig DNA were found in some burgers.
It appears that "traces" of pig DNA were also found in 85% of the burger products tested. The fact that only traces were detected suggests to me that either a pig-derived additive was used in the manufacture of the burgers, or the beef was ground in equipment improperly cleaned after processing pork. This latter suggestion is perhaps unlikely, as the traces were found in burgers supplied by a number of manufacturers.
In itself, the finding of traces of DNA from meat animals other than beef cattle should not be cause for alarm - no harm can come from consuming the burgers. However, some religious and cultural sensibilities may be offended - if you are not allowed to eat pork for whatever reason, you should be able to purchase "beef" products with the expectation that they don't contain pork. Of course, 30% horse meat in a beef burger is not a trace and the implication is that in this case there was a deliberate attempt to deceive the customer.
While I don't condone the addition of meats not appearing on the label, I wonder if this is another of those situations where the use of highly sensitive analytical techniques has raised a storm. Something similar happened many years ago when milk was tested by a new, sensitive method for detecting dioxin. In that case, the dioxin came from the chlorine-bleached paperboard used in manufacture of the milk cartons and was at extremely low levels in the milk.
How many other foods that we take for granted contain minuscule traces of DNA, and, by implication, foreign plant or animal materials, which get there as a result of the use of natural additives?
The Irish Agriculture Minister, Simon Coveney, has blamed a single meat processor and has further stated that the horse meat entered the product via an imported additive, though the nature or identity of the additive was not mentioned.
You can't tell by looking at a burger just what sort of meat is present, so some fairly sophisticated laboratory methods must be used. Though not stated in the press articles I have read, the chances are that the burger was tested for specific DNA markers for horse meat. Indeed, both horse and pig DNA were found in some burgers.
It appears that "traces" of pig DNA were also found in 85% of the burger products tested. The fact that only traces were detected suggests to me that either a pig-derived additive was used in the manufacture of the burgers, or the beef was ground in equipment improperly cleaned after processing pork. This latter suggestion is perhaps unlikely, as the traces were found in burgers supplied by a number of manufacturers.
In itself, the finding of traces of DNA from meat animals other than beef cattle should not be cause for alarm - no harm can come from consuming the burgers. However, some religious and cultural sensibilities may be offended - if you are not allowed to eat pork for whatever reason, you should be able to purchase "beef" products with the expectation that they don't contain pork. Of course, 30% horse meat in a beef burger is not a trace and the implication is that in this case there was a deliberate attempt to deceive the customer.
While I don't condone the addition of meats not appearing on the label, I wonder if this is another of those situations where the use of highly sensitive analytical techniques has raised a storm. Something similar happened many years ago when milk was tested by a new, sensitive method for detecting dioxin. In that case, the dioxin came from the chlorine-bleached paperboard used in manufacture of the milk cartons and was at extremely low levels in the milk.
How many other foods that we take for granted contain minuscule traces of DNA, and, by implication, foreign plant or animal materials, which get there as a result of the use of natural additives?
Monday, January 7, 2013
Fancy a snot pie?
The thought of this is totally gross. Why would I contemplate writing under such a heading?
Unfortunately, it's quite possible that some customers have in fact been sold pies contaminated by the profuse nasal secretions of a baby held in the arms of the cook filling the pies. Talia Shadwell wrote a piece in the Manawatu Standard at the end of December 2012 about a family-owned Rangitikei food premises forced to close because of a very unfavourable food safety inspection report. In addition to the highly probable contamination of the pies by the infant, the milkshake blender was encrusted with rotten milk. It is likely that there were other violations of good catering practice and the Food Hygiene Regulations.
Legislation is changing in New Zealand, but it is safe to say that the intent of the regulations will not change. District councils are responsible for registering food premises and it is illegal to sell food not produced in registered premises.
"No persons shall be issued with a Certificate of Registration for food premises (except a vehicle used solely for the carriage or delivery of food for sale) unless -
Unfortunately, this state of affairs is probably more common than we would like to think - many food premises are run by immigrants who provide the rich diversity of foods available in New Zealand, but who may have very limited knowledge of the language and regulations. This is no excuse for poor hygiene and food production practices.
Consumers have a right to expect their food to be safe to consume and to be produced under aesthetically acceptable conditions.
Unfortunately, it's quite possible that some customers have in fact been sold pies contaminated by the profuse nasal secretions of a baby held in the arms of the cook filling the pies. Talia Shadwell wrote a piece in the Manawatu Standard at the end of December 2012 about a family-owned Rangitikei food premises forced to close because of a very unfavourable food safety inspection report. In addition to the highly probable contamination of the pies by the infant, the milkshake blender was encrusted with rotten milk. It is likely that there were other violations of good catering practice and the Food Hygiene Regulations.
Legislation is changing in New Zealand, but it is safe to say that the intent of the regulations will not change. District councils are responsible for registering food premises and it is illegal to sell food not produced in registered premises.
"No persons shall be issued with a Certificate of Registration for food premises (except a vehicle used solely for the carriage or delivery of food for sale) unless -
• That person has been issued with a Council recognised Certificate in Food Hygiene or another qualification approved by Council; orIt is perhaps surprising that the inspection report noted that the family had 'very limited' knowledge of food hygiene and food safety practices.
• There is, working on the food premises, a Manager or a staff member with specific responsibility for staff training in food hygiene, who has been issued with a Certificate in Food Hygiene, a Certificate in Basic Food Hygiene or other qualification approved by Council."
Unfortunately, this state of affairs is probably more common than we would like to think - many food premises are run by immigrants who provide the rich diversity of foods available in New Zealand, but who may have very limited knowledge of the language and regulations. This is no excuse for poor hygiene and food production practices.
Consumers have a right to expect their food to be safe to consume and to be produced under aesthetically acceptable conditions.
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