Analysis of DNA isolated from different oil sources: problems and solution

Background: One of the major aspects of traceability in food authenticity assessment is to explore practical methods to find the origin of food. Objective: The aim of the present study was to find a DNA based method for authentication and traceability of food, which are of great importance in health management. Methods: Four different DNA extraction methods were applied to obtain high pure DNA in some oil samples including olive oil, sunflower, canola and soybean oil to improve the traceability. The isolated DNA was analyzed by PCR using common primer pair, derived from the region harboring 18S rRNA/5.8S rRNA genes. Extraction methods were developed based on specific binding of DNA molecules to the silica membrane (column) or resin. Results: Our results showed that amplifiable DNA could only be extracted from olive oil in method 1, whereas the isolated DNA from other samples needed to be purified. In method 2, by pre-treating of oil with PBS and subsequent precipitation with Isopropanol, the amplification of isolated DNA was observed in sunflower, crude canola and olive oil. To remove more effectively the contaminants, method 2 was combined with chloroform and resin/Isoporopanol precipitation as method 3. Interestingly, the extracted DNA from all examined oil samples could be amplified with mentioned primers. For elimination the disadvantages of chloroform, method 4 was set up by direct usage of lysis and binding buffer. The extracted DNA from all refined oil samples could be amplified successfully. Conclusion: Based on our findings, the major problem in DNA extraction from oils is the PCR inhibitors in extracted DNA, which can be resolved by the presented methods 3 and 4.