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.