-Caveat Lector- http://www.the-times.co.uk/news/pages/sti/99/09/05/stiinnnws01007.html?19023 95 September 5 1999 INNOVATION Genetic modification Simple test will let shoppers check produce for GM content AN INSTANT test for GM foods could soon allow shopkeepers and customers to check whether produce is totally free of modified crops, writes Roger Dobson <mailto:[EMAIL PROTECTED]>. One of the problems with GM products is that it is difficult to tell them apart from natural foods. Many processed foods thought to be GM-free have been found to contain small amounts of engineered material. It is possible to carry out DNA tests to spot the difference in the crop gene, but that is time-consuming, expensive and often impractical. The new test, developed by Strategic Diagnostics of Delaware in America, adapts the kind of antibody technology first used in DIY pregnancy kits to track down the genetically modified crops. The key to the success of the tests is that crops that have been genetically engineered produce a different type of protein. A plant engineered to be resistant to a specific insect, for instance, will express a protein toxic to that pest. With a herbicide-resistant crop, the plant will express a protein that de-activates the effect of the chemical. The test developed by Strategic Diagnostics measures these proteins, which would not be expressed by a normal plant. One test can measure the actual amount of protein in the sample, while the other is a yes-no litmus-paper type test that simply shows in minutes whether there is any GM food present. Don Durandetta, business manager for agricultural products at Strategic Diagnostics, says that unlike DNA tests, which are looking for the gene that creates the protein, the new test measures the protein directly and is much faster. He says: "The yes-no test takes only four or five minutes to give a result. It is essentially the same format as a standard home-pregnancy kit." The testing strip contains antibodies that are specific to the protein being looked for. On one side is a monoclonal antibody and on the other a polyclonal antibody. Attached to one of them is a colour marker. When the strip is immersed in the crop sample that has been mixed with water to make it fluid, the sample flows along a line between the arrays of antibodies. When the protein to which the antibodies react passes along the line, the antibodies on either side close in and form a sandwich, triggering the marker and changing the colour of the strip. "It is a simple yes-no sandwich assay test and the only way you can end up with a coloured strip is if both antibodies respond and a sandwich forms to change the colour, and that shows that there is transgenic protein present. This particular test doesn't tell you how much there is, just whether or not there is any present in the sample. "The first applications are at the producer end. Our biggest market at present is the quick yes-no test, which can screen trucks as they roll up from the farm. You can test a truck while it is still on the scales. You can take raw grain out of trucks as they arrive, grind it up, shake it up with water, take a sample and drop a strip in. It takes three or four minutes and the whole process, including gathering the sample, takes six minutes." The company is currently testing the effectiveness of the strips on processed products. If found to be useful, this could lead to a consumer version that could quickly tell shoppers if food contains any kind of GM-modified ingredients. One of the advantages for food producers is that the test will allow them to guarantee that there is no GM material in their crops. For food suppliers and shops, it means that they will be better able to put similar guarantees on processed-food packaging. Eventually, the antibody technology could be applied to many other forms of GM food as they start to come onto the market. With new GM legislation likely in Europe, Japan and America, the tests could protect producers from legal action where food that is meant to be GM-free is found to have a transgenic content. It would also mean that such food would not have to be junked as was the case in America when thousands of boxes of organic crisps were destroyed because the corn used had been accidentally contaminated by a crop from a neighbouring field of transgenic plants. Copyright (c) 1999 Times Newspapers Ltd. ======================= Robert F. Tatman Computer Help Desk Desktop & LAN Services Systems Department Philadelphia Newspapers, Inc. 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