Influence of different oil-refining parameters and sampling size on the detection of genetically modified DNA in soybean oil

The degumming of crude soybean oil causes the removal of DNA, the presence of which is necessary for the detection of genetically modified organisms by polymerase chain reaction (PCR). In both chemical and physical refining processes, physical conditions of the refining steps can vary within a certain range. The extremities in this range may have a different influence on the quality and quantity of the extracted DNA. Therefore, the effects of degumming temperature, degumming time, and the amounts of water and/or acid added during degumming on the DNA quality and amplification were evaluated. Some parameters were shown to have a small influence on the quality of the DNA, but none affected the amplification of soy DNA extracted from the water fractions after the degumming. From the oil fractions, no DNA could be visualized. In this study of the ability of the degumming process to achieve the total removal of DNA from the oil fractions, the sample size during DNA extraction was increased significantly, and amplification of the soy lectin genes was attempted. This resulted in a positive amplification of the lectin gene. A possible relation between the size of the test portion, the residual phosphorus content of the sample, and the PCR result is suggested.