The Fate and Degradation of Genetically Modified Soybean DNA Along the Soybean Oil Processing Chain: Quantitative Tracking and Comparison of Degumming Methods

Soybean is the most widely cultivated genetically modified (GM) crop worldwide, making the detection of GM soybean oil a critical issue for food safety and trade compliance. Such detection depends on whether DNA survives oil processing, yet how processing affects DNA in refined oil has remained unclear. Here, we tracked DNA mass and gene integrity along a complete industrial soybean oil processing chain, from seed to deodorized oil, and compared three degumming methods at laboratory scale. DNA mass dropped sharply during crude oil extraction and degumming, the larger part of the loss occurring between the meal and the crude oil, leaving refined oils with extremely low levels (2.60 × 10−2 to 7.43 × 10−1 ng/g). During degumming, most DNA moved from crude oil into the oil sediment, with removal efficiency decreasing in the order enzymatic > acid > hydration degumming, in line with phospholipid removal. The lectin and cp4 epsps genes degraded mainly during solvent extraction and deodorization. These findings reveal where GM DNA is lost or destroyed along the chain, show that fragments below 200 bp survive to fully refined oil, and identify enzymatic degumming as the most effective treatment for removing DNA (at the lab scale). Testing of refined soybean oil therefore requires short amplicons, and a negative result obtained with longer targets does not demonstrate the absence of GM material.