Oxidative reactivity of unsaturated fatty acids from sunflower, high oleic sunflower and rapeseed oils subjected to heat treatment, under controlled conditions

The oxidation kinetics of three vegetable oils (sunflower, high oleic sunflower and rapeseed) were followed during heat treatment (100 °C, 120 °C and 150 °C for 6 h), in the absence or presence of α-tocopherol (around 15 × 10−4 mol L−1) or a mixture of α-tocopherol and chlorogenic acid (around 15 × 10−4 mol L−1 of each). The kinetics were followed by measuring several chemical markers: fatty acids, conjugated dienes, hydroperoxides and aldehydes. The results showed that the unsaturation degree of the oils tested was the predominant parameter influencing the progress of oxidation kinetics. In this sense, sunflower oil was systematically more oxidized than rapeseed oil, which itself was more oxidized than high oleic sunflower oil.Oxygenation conditions and oil temperature were also determinant inducers of oxidation. The addition of α-tocopherol significantly delayed the formation of oxidation products while chlorogenic acid did not enhance the oxidative stability of oils but protected α-tocopherol during heating.

► Kinetics of oil oxidation are modelled using a quadratic regression method.
► Oxidation of oil during heating is mainly influenced by its unsaturation degree.
► Surface of exchange of oil with air is a key inducer of oxidation at high temperature.
► α-tocopherol significantly delays the production of lipid oxidation products.
► Chlorogenic acid preferentially acts as a protector of α-tocopherol.