Model Systems for Developing Detection Methods for Foods Deriving from Genetic Engineering

Model systems for investigating the influence of the food matrix and depth of processing on detection limits for foods deriving from genetic engineering were established using the phytase-encoding gene ofEscherichia coliATCC 33965. For detection the polymerase chain reaction was applied directly to DNA extracted from foods based on cereals.E. colicells andE. coliDNA were added to musli, rolled oats, and rye flour in concentrations of 1010to 102CFU and 10 mg to 10 pg per gram, respectively. After soaking of the food samples in water or yoghurt, detection limits were determined to be 103to 104CFU and 10 to 100 pg by specific DNA hybridization. After sourdough fermentation of rye flour a hybridization signal was observed only with rather highE. coliconcentrations (>1010CFU), whereas detection was impossible in ready-baked breads.