Detection of seven genetically modified maize events in foog products on the portuguese market
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abstract
Maize, the second most important genetic modified (GM) crop, has the highest number of authorized GM events for food and feed in EU. Since the GMO entered the food chain, the EU has dedicated special attention to consumer information by requiring a compulsory labelling for food products containing more than 0.9% of GM material. The need to monitor and verify the presence of low levels of biotechnology-derived material in complex food products demands sensitive and highly specific analytical methods. Most methods for GMO detection and quantification are based on polymerase chain reaction (PCR), since protein-based assays are not suitable for processed food.
The aim of the present work was to isolate DNA from a range of maize foods, to screen for the presence of GMO, to detect specific GM events and finally confirm and quantify the positive results. The screening of GM products was carried out by qualitative PCR targeting the 35S promoter and the NOS terminator. For the positive results, two types of PCR assays were applied and adapted for each GM event tested: qualitative PCR for the specific detection and real-time PCR with TaqMan probes for confirmation and quantitative purposes. The GM maize events analysed were Bt11, MON810, E176, GA21, MON863, NK603 and TC1507.
The screening results evidenced a considerable level of contaminated food products (grains, flours, snacks, cornflakes, cereals, biscuits, etc.) in the Portuguese market. From the events analysed, TC1507, MON810 and Nk603 were the most frequent. The quantitative results indicate that a more severe control should be applied, as two of the products included levels above 0.9%, and none of the food products was labelled for the presence of GMO.
