Using PCR testing to Detect Foods With Unlabeled GM Ingredients

Before 2009 Turkey had minimal regulations of genetically modified foods. In a study containing 26 processed saybean, maize, cotton, and canola products, Arun et al. (2013) found that 42.3% were positive for GM ingredients. After regulations went into place, the authors reevaluated the amount of GM ingredients in foods using a polymerase chain reaction (PCR) test. The authors found that of 100 samples only 25 contained GM ingredients, a significant decrease since the 2009 study.  After evaluating results before and after GM regulations went into place, the authors conclude the regulations have been sufficient in decreasing the amount of unlabeled GM ingredients in food. These results show the effectiveness of regulating GMOs during importation and that PCR is a sufficient way to test for GMOs in food.—Morgan Beltz
Arun, O., Yilmaz, F., Muratoglu, K., 2013. PCR detection of genetically modified maize and soy in mildly and highly processed foods. Food Control 32, 525-531.

                  Arun et al. collected 100 different processed food samples that contained maize, soy, or both. The authors used certified reference materials consisting of soybean powder and maize powder as negative and positive controls for comparison with the samples. For the mildly processed samples and controls the authors extracted and purified DNA using the Promega Wizard DNA isolation kit. Highly processed samples had DNA extracted using the cetyltrimethyl ammonium bromide method and then purified with the Promega Wizard DNA isolation kit. The extracted DNA from each sample was primed in a PCR for an amplification reaction. This process allowed the authors to target a specific strand of DNA in each sample to study it. Each amplified DNA strand was separated and stained through electrophoresis in gel that had ethidium bromide in order to view the macromolecules in the DNA strands. To account for false negatives the authors analyzed each negative sample further for presence of soy lectin and maize zein sequences which are present in all GM foods. The authors also put a cauliflower mosaic virus (CaMV) (a virus that almost all GM food contains) 35S promoter in control samples to compare to false negative results related to PCR inhibitors.
                  The authors found that 14 of 43 maize samples and 11 of 57 soy samples tested positive for GM ingredients, 25 percent overall. Sixty-three negative samples were confirmed as true negatives with specific amplification of the lectin and zein sequences. The other 12 negatives were negative for both lectin and zein, suggesting that they had little or no soy or maize DNA present.The authors also found that three of the 14 positive samples contained two different GM strands, not uncommon, as other studies have found. Arun et al.did have difficulty extracting DNA from 5 negative lectin soy samples, as have other researchers, but the samples were evaluated again to make sure the negatives were not false.
These results are similar to those found in other studies conducted after new regulations are imposed. Other researchers reported having similar problems with DNA extraction with high processed foods, having so many negatives, and having negatives that did not have any detectable maize and soy DNA. This leads the authors to believe that the extraction process can be improved. However, the consistency with other studies shows the accuracy of PCR testing and effectiveness for tracing GM foods through to importation.

Although it is positive that the regulations have led to a decrease in unlabeled GM foods, some remain in the market, leading the authors to call for additional regulations and stricter enforcements. The success of this PCR study shows the authors that it is an effective way to monitor the GM content in unlabeled foods.

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