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 degrees C, 120 degrees C and 150 degrees C for 6 h), in the absence or presence of alpha-tocopherol (around 15 x 10(-4) mol L-1) or a mixture of alpha-tocopherol and chlorogenic acid (around 15 x 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 alpha-tocopherol significantly delayed the formation of oxidation products while chlorogenic acid did not enhance the oxidative stability of oils but protected alpha-tocopherol during heating. (C) 2013 Elsevier Ltd. All rights reserved.