Abstract
A method using polymerase chain reaction (PCR) was designed for the detection of food or food ingredients derived from genetically modified soybeans (GMS), imported from the United States, in a mixture with conventional non-genetically modified soybeans (non-GMS). The presence of recombinant deoxyribonucleic acid (DNA) in the soybeans could be detected with three different pairs of specific oligonucleotide primers designed from the sequences of the introduced genes. The soybean intrinsic lectin Le1 gene was used as an internal control. The results of the PCR amplification indicated that a method using cetyltrimethylammonium bromide (CTAB) was most suitable for DNA extraction from soybeans and the processed foods. The recombinant DNA could be detected in dry soybeans containing 0.05% GMS and tofu made from soybeans containing 0.5% GMS. Of 41 commercial tofu samples, recombinant DNA was detected from 27 tofu samples. It is, however, difficult to carry out PCR on DNA extracted from soybeans steamed at 131°C or on fermented natto, although the Le1 gene was detected from soybeans steamed at 115°C and in the fermented natto when a nested PCR technique was employed.
