Wednesday, July 17, 2013

DNA Barcoding and olive oil

Do you cook? Of course I mean real cooking not heating up a pre-processed meal. I love cooking from scratch and use fresh and largely unprocessed ingredients. In this regard you might understand my fondness for olive oil. To me it tastes better than many other oils and it also has been associated with a lot of health benefits. Preliminary clinical studies have provided evidence that consumption of olive oil may lower the risk of heart disease through factors such as lower blood cholesterol levels and reduced LDL cholesterol oxidation. Pilot studies also showed that olive oil may affect oxidative damage to DNA and RNA, revealing a possible carcinogenic factor.

Such benefits make good olive oil more expensive than other vegetable oils which unfortunately makes it particularly prone to fraudulent practices. It is frequently blended with lower-cost oils of plant origin, such as soya (Glycine max), canola (Brassica napus), maize (Zea mays), sunflower (Helianthus annuus), and even sesame (Sesamum indicum) oils. 

So far adulteration of plant oils was mainly determined with analytical chemistry methods with limits of detection of around 5%. There is a clear need for a reliable, more sensitive method to detect the botanical origin of oils and oil mixtures. To me this sounds like a case for DNA Barcoding and indeed some researchers from Greece have put it to the test. They explicitly tested a high-resolution melting analysis-based method (HRM) using the rbcL barcoding region as target to obtain barcoding references for the major vegetable oil species and to quantitatively identify the botanical origin of plant oils. They also tested various mixtures of olive and canola oil to demonstrate the applicability of HRM for the detection of adulterants. The new method was capable both of distinguishing among different vegetable oil species and detecting a level of 1% of canola oil in olive oil. 

Very promising and given the relatively low cost of HRM methods very reassuring as this method could be easily adopted in regular food inspections. I very much like the idea of having good and more importantly pure olive oil in our meals. And by the way - always use cold pressed extra virgin ones.

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