Oxidative stabilities of olive and camellia oils: Possible mechanism of aldehydes formation in oleic acid triglyceride at high temperature

Olive and camellia oils were monitored and compared during heating at 120 °C, 150 °C and 180 °C for 24 h to determine the possible thermal oxidation mechanism of oleic acid triglyceride. The results demonstrated that octanal, nonanal, decanal, 2-decenal and 2-undecenal were the characteristic carbonyls for oleic acid-rich oils. The oxidation rule of oil was easily determined at 120 °C, at which point changes in the acid value, peroxide value, anisidine value and carbonyl compounds corresponded to changes in fatty acids and tocopherols. However, the oxidation rule of oil was different at higher temperatures. According to the evolution of five characteristic aldehydes, four types of oxidation pathways of oleic acid triglyceride were obtained: Decanal and 2-undecenal came from the homolysis of 8- hydroperoxide. Nonanal was from the homolysis of 10- hydroperoxide and 9- hydroperoxide. Octanal was from the homolysis of 11- hydroperoxide. 2-Decenal was from the homolysis of 9- hydroperoxide. Homolysis B-scission of 10-hydroperoxide (nonanal), 11-hydroperoxide (octanal) and 8- hydroperoxide (decanal) was predominant at 120 °C, but was weakened as the temperature increased to 180 °C. Hence, the temperature had a significant effect on the formation and decomposition of hydroperoxide positional isomers.