IDENTIFYING GENETICALLY MODIFIED ADULTERANTS IN OLIVE OIL USING PCR AND ELECTROPHORESIS

The increased world-wide demand from consumers for high quality olive oil coincides with the rising level of adulterated olive oil products being imported into the United States. Olive oil adulterants most commonly consist of canola and soybean oils, 85-95% of which contain genetically modified (GM) ingredients. This investigation describes a method for identifying olive oil adulterated with genetically modified oils utilizing PCR and agarose gel electrophoresis. Given that the most prevalent promoter used in the development of GM plants is the cauliflower mosaic virus 35S promoter (CaMV35S), this was chosen as the target sequence for DNA amplification via PCR. One organic olive oil, two conventional olive oils, and one conventional canola-soybean oil were purchased at a retail store and tested for the presence of the CaMV35S promoter. Following ethanol extraction, DNA samples were amplified using PCR. The amplified samples were run on a 2.4% agarose gel and observed for the presence of the fragment indicative of the CaMV35S promotor. Both the organic olive oil and the conventional canola-soybean oils tested positive for the promoter found in GM plants. It was not surprising to find evidence of GM oil in the conventional canola-soybean oil since most soy and canola produced world-wide are GM. Since olives are not genetically modified, the positive result in the organic olive oil indicates the presence of GM DNA and suggests that the olive oil has been adulterated with a GM plant oil. These data indicate that PCR can be utilized to identify olive oil adulterated with GM products. Further testing may demonstrate that PCR analysis will provide a simple, reliable, and reproducible method for rapid analysis of the purity of olive oil.