If a proof was needed, a Moroccan research confirms what we have known since a long time!
The extra virgin olive oil is the healthiest for cooking and the one that is more resistant to high temperatures. A recent article in the magazine Teatro Naturale tells us how the research has compared what happens to extra virgin olive oil and olive oil after prolonged thermal stress. The performances of extra virgin olive oil are indisputably superior and this is due to the content of a-tocopherol and polyphenols. In this screenshot the test result of the research conducted:
The heat treatment imposed on the two oils was very severe and conducted with a Rancimat apparatus, with 100 degrees of temperature, with air flow of 10 liters / hour for a total of 120 hours.
Extra virgin olive oil has a higher content of antioxidant compounds, capable of protecting the unsaturated fatty acids from deterioration. As expected, at the end of the thermal stress, the content of polyphenols and tocopherols for both oils was reduced almost to zero. The test result indicates that olive oil degrades more than the extra virgin, after prolonged and severe heating. Oxidation, without tocopherols and polyphenols to protect the oils, proceed in a much more intense way in olive oil, with a significant impact on the unsaturated fatty acids.
Source: Said Gharby, Hicham harhar, Bertrand Matthäus, Zakia Bouzoubaa, Zoubida Charrouf, The Chemical Parameters and Oxidative Resistance to Heat Treatment of Refined and Moroccan Picholine Extra Virgin Olive Oil, Journal of Taibah University for Science, Available online 20 July 2015