Detection of genetically modified soybean DNA in refined vegetable oils

In this study, four different protocols were tested for their ability to extract DNA from blended refined vegetable oils: the in-house prepared Wizard and CTAB methods and the methods based on the use of the commercial kits Wizard(A (R)) Magnetic DNA purification system for food and Nucleospin(A (R)) for food. The performance of the extraction protocols was determined by end-point polymerase chain reaction (PCR) targeting the soybean lectin gene with primers suitable for the amplification of small fragments and confirmed by real-time PCR with specific hydrolysis probes. From the tested protocols, the Nucleospin method was the only one able to produce amplifiable DNA from refined vegetable oils. To verify the presence of Roundup Ready(A (R)) (RR) soybean, event-specific primers were used for end-point PCR assays. The amplification of trace amounts of RR soybean by real-time PCR confirmed the label statements of two samples. The results highlight the importance of the DNA extraction protocol and the critical choice of PCR primers on processed food matrices, such as refined oils. Considering the few reports and difficulties pointed out in the literature to obtain amplifiable DNA from refined vegetable oils, the present results can be a step forward in the traceability of refined oils regarding authenticity issues and genetically modified organism detection.