Changes in unsaturated fatty acids during heating treatment. When evaluating changes in fatty acids profile during heating of the frying oils, there was a difference in the unsaturated fatty acid composition depending on the oil nature. This composition decreased when time of frying increased. A significant difference was observed between oils after 24 h of heating (p < 0.05). Oil treated with RE conserves the higher amount of unsaturated fatty acids even after 30 h of heating which suggests that this oil resist to oxidation.
Therefore, this can prove the action of the phenolic extract to inhibit the unsaturated fatty acids oxidation. It has been already demonstrated that the involvement of phenolic compounds in the oxidation chain can be done in two ways: some of them inhibit the propagation of radical reactions, others prevent the free radicals formation which are the initiators of the oxidation reaction. It was also proved that the phenolic compounds of the rosemary are active against oxygen free radicals involved in the initiation of radical reactions. In addition, some phenolic compounds may react with metals known
as initiators of lipid oxidation, they are active as metal chelators and can prevent the oxidation process