DNA chip will catch beefed up chicken

March 03, 2004

HAS your chicken been bulked up with beef or pork extracts? Is that expensive albacore tuna really cheap skipjack tuna? Did rats, mice or even bits of people fall into the mincer when your burger was being made? And are unscrupulous companies risking spreading mad cow disease by adding beef to cattle feed?

All these questions can now be answered by a single test that reveals the presence of meat from any of 32 different species in food samples.

The test, based on a DNA chip, is being evaluated by food regulatory authorities in Europe, and could also be used by supermarkets and food companies to check on their suppliers.

"The beauty of this is that you can scan for so many things at once," says Thomas Schlumberger, director of clinical genetics at Affymetrix in California, which developed the "FoodExpert-ID" chip together with bioMérieux of France.

The chip's main use would to ensure meat products are what they say they are and don't contain anything they should not. It can reveal, for example, whether foie gras päté really contains goose liver.

The test could also help expose scams like the one uncovered in Europe last May, in which a few poultry producers were caught bulking up chicken meat with beef and pork waste.

As well as posing a possible BSE risk, the scam also meant that people whose religions forbid eating pork may have ended up consuming it.

The UK's Food Standards Agency says that it is evaluating the potential of the test and comparing it with a more experimental system built by Agilent of California. However, determined food fraudsters may be able to outwit the chip.

It has been claimed that some producers are treating beef or pork extracts to destroy the DNA before they add them to other meats. If the chip takes off, its first specific task is likely to be ensuring that cattle feed is free of any illegal animal remains that might spread BSE.

In the US, which reported its first case of BSE in December, the Department of Agriculture may consider evaluating the test. It is being assessed in Europe, where all animal remains have been banned from feed since 2000. Trials are planned this year in the UK, the Netherlands and France.

"We would find this very valuable if it does what it's meant to," says a spokesman at the UK's environment ministry. DNA microarray chips have long been used in the lab (New Scientist, 14 November 1998, p 46), but Affymetrix claims the FoodExpert-ID is the first mainstream commercial application of the technology.

The chip's surface sports segments of DNA unique to each species (see Table) arranged into discrete zones. DNA strands from the food sample are transcribed into RNA and tagged with fluorescent chemicals.

These are then washed over the chip. Any matching sequences stick together, so the pattern of fluorescent zones read by a laser scanner reveals which species are present.

Schlumberger estimates the cost of all the equipment needed to perform the tests is around €250,000, but each test would cost only €350 to €550. Future generations of the chip could include DNA from an even larger number of species.

Affymetrix expects its microarrays to become the "Intel chips of microbiology", and is developing similar devices with Roche Diagnostics of Switzerland to diagnose human cancers and viruses such as HIV.
New Scientist issue: 6 March 2004

Written by Andy Coghlan


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