Is food less safe these days? Part 1

Over the Christmas period I have done a lot of eating and drinking and being merry. I’ve also done a lot of thinking about food safety. In the last year we seem to have read almost daily of Listeria being found in deli meat, that babies have been poisoned by formula milk, children have been hospitalized with failing kidneys resulting from Escherichia coli O157:H7 infection, that melamine has turned up in yet another food product, or that an established company has closed its doors because of massive losses resulting from a food recall. Is our food less safe these days?

I don’t think that there is a simple answer, but I do have some suggestions. In this three-part posting I’ll share them with you.

I think that the whole thing can be analysed under a few subheadings.

Food Preparation: Some of my Christmas celebrations have involved large functions where caterers have served meals to hundreds of partygoers. These meals could not have been produced on the premises, so the food must have been pre-prepared and transported to the venue in insulated containers or perhaps reheated before serving. Other celebrations have been more modest, catered by the “bring a plate” approach. We have had barbecues, where foods were cooked outside on gas or charcoal burners. All of these scenarios have at least one thing in common – the foods were prepared by others for us, perhaps in non-ideal conditions, or were not eaten immediately after preparation. The opportunities for contamination of the food, incomplete cooking and growth of bacteria were numerous.

Centralization: The economies of scale lead to evolution of very large manufacturing operations with huge distribution networks. Smaller companies are squeezed out of the market. If something goes wrong in this supply chain, the impact can be widespread. In 2000, Staphylococcus aureus bacteria built up in raw milk that was unable to be cooled for several hours after fat separation in Snow Brand's Taiki factory. Ultimately, at least 14,700 people, mostly in western Japan, were affected by food poisoning after consuming milk or related products made by the company. Topps Meat Company, a US company specializing in manufacture of frozen ground beef, recalled 21.7 million pounds of ground beef, bringing the total recalls in the US between April and October 2007 to over 30 million pounds of red meat, mostly hamburger. The reason was that there had been a number of cases of Escherichia coli O157:H7 infection tied to its products. There was evidence of an inability to identify unique batches of product and this probably contributed to the size of the recall. The USDA also cited the company for “inadequate process controls in the non-ground meat production line”.

Ignorance may play a part. Last Easter in New Zealand, 22 people were poisoned, some seriously, when they consumed comb honey which had been made by bees that collected honeydew from tutu plants (Coriaria arborea) infested by vine hoppers. The upshot was that the honey contained large amounts of the toxin tutin, which is found in the sap of the tutu plant. In April last year, I wrote that this was not a new problem. See here Indeed, F.S. Fastier, Roslyn Emeritus Professor of Pharmacology at University of Otago, wrote last week that he was present at a meeting of interested parties in Wellington in 1964, where the issue was debated. Beekeepers have known how to manage this hazard for a long time, but a small beekeeping operator last year apparently failed to take account of the fact that there were tutu bushes in flower in the bees’ foraging area and continued to sell the comb honey. The resulting poisonings have led to the New Zealand Food Safety Authority introducing legislation to limit the amount of tutin that may be present in honey offered for sale. See here
This has not pleased everyone – some think the regulations don’t go far enough, some in the industry consider them to be unnecessary. However, NZFSA could not stand by and do nothing without risking the health of the population and the future of the lucrative New Zealand honey industry. The regulations will be reviewed at the end of the 2009 season.


In Part 2: click here:  Globalization and Greed

Melamine

Perhaps, like me, you have been wondering why some unscrupulous Chinese suppliers would put plastic first into pet food (2007) and then milk (2008). The extent of my knowledge was that melamine is a monomer used in making hard plastic products as diverse as bowls, shoehorns and bench coverings. It seemed to me that such a compound would be more expensive than the product it was substituting and thus not worth the effort. So I did a little searching on the Internet.

There is some confusion in terminology. Melamine is a ring structured compound containing a lot of nitrogen (66% by mass). It is combined with formaldehyde to produce melamine resin, a thermosetting plastic. However, the plastic is also often called simply “Melamine”. There are a number of ways of making the monomer; these days it is usually made from urea, but it can also be made from coal. China is the largest producer of melamine in the world.

The current story probably has its origins in a patent from 1958, which described the use of melamine as a source of non-protein nitrogen in cattle feed. However, a study conducted in 1978 suggested that melamine is digested more slowly and less completely than cottonseed or urea, so its use is probably limited.

Melamine itself has a low toxicity – approximately the same LD50* as sodium chloride. However, the combination of melamine and cyanuric acid in the diet causes acute renal failure in cats. This came to light after the contaminated pet food incident. I think it is unlikely that many humans consume cyanuric acid in their diets, though this compound has been approved by FDA for use in animal feed and is used as a precursor to N-chlorinated cyanurates, which are used to disinfect water e.g. in spa and swimming pools. Chronic ingestion of melamine can lead to formation of kidney and bladder stones and it may be that this is a particular problem in very young children.

Perhaps the reason for the adulteration of the Chinese products was that melamine can increase the apparent protein content of the food. It has been reported that melamine scrap is widely incorporated into livestock and fish feed in parts of China (New York Times, 30th April, 2007). Since “melamine scrap” is an impure and less valuable form of the chemical produced as a by-product, for example in coal gasification, this could explain why it might be economical to replace milk or meat protein with this non-protein nitrogen source if it can be concealed from the authorities and customers. Measurement of protein content by the Kjeldahl or Dumas methods, which actually measure nitrogen content, would not detect the adulteration. Testing for melamine directly is difficult and expensive, though test kits are now available.

As an aside, since melamine is used in food packaging and tableware, small amounts of the compound (parts per million level) may be found in foods and beverages as a result of migration from melamine polymers in contact with the food. These levels are not considered to be a health risk.

* LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals.