Detection of genetically modified Bt maize in cooked food products by PCR

A comparison was made of eight known and published PCR primer sets to detect zein, cryIA(b), bla and bar genes and the 35S cauliflower mosaic virus promoter of transgenic Bt "Maximizer" maize "event 176" (Novartis) in cooked food products. Transgenic pop corn, polenta and cookies were used as models. The polenta and cookies were made with different percentages (100, 1, 0.1% w/w) of transgenic maize flour. The DNA extracted from samples taken at different times of cooking revealed a progressive decrease in the average DNA fragment length, which was, however, still amplifiable by PCR. Of the primer sets tested, Cry 03/04 showed the best performance and led to the detection of transgenic DNA in final cooked products containing of Bt-maize DNA as low as 0.1%.