Applicability of the quantification of genetically modified organisms to foods processed from maize and soy.

The applicability of quantifying genetically modified (GM) maize and soy to processed foods was investigated using heat treatment processing models. The detection methods were based on real-time quantitative polymerase chain reaction (PCR) analysis. Ground seeds of insect resistant GM maize (MON810) and glyphosate tolerant Roundup Ready (RR) soy were dissolved in water and were heat treated by autoclaving for various time intervals. The calculated copy numbers of the recombinant and taxon specific deoxyribonucleic acid (DNA) sequences in the extracted DNA solution were found to decrease with time. This decrease was influenced by the PCR-amplified size. The conversion factor (Cf), which is the ratio of the recombinant DNA sequence to the taxon specific DNA sequence and is used as a constant number for calculating GM% at each event, tended to be stable when the sizes of PCR products of two DNA sequences were nearly equal. The results suggested that the size of the PCR product plays a key role in the quantification of GM organisms in processed foods. It is believed that the Cf of the endosperm (3n) is influenced by whether the GM originated from a paternal or maternal source. The embryos and endosperms were separated from the F1 generation seeds of five GM maize events, and their Cf values were measured. Both paternal and maternal GM events were identified. In these, the endosperm Cf was lower than that of the embryo, and the embryo Cf was lower than that of the endosperm. These results demonstrate the difficulties encountered in the determination of GM% in maize grains (F2 generation) and in processed foods from maize and soy.