Novel approach to evaluate the oxidation state of vegetable oils using characteristic oxidation indicators.

Four vegetable oils with typical fatty acid compositions were chosen to determine their indicators of lipid oxidation under the conditions of accelerated oxidation. Good linear correlations were observed between the total nonpolar carbonyl amount and the total oxidation value (TOTOX, R(2) = 0.89-0.97) or peroxide value (POV, R(2) = 0.92-0.97) during 35 days of accelerated oxidation. Additionally, nonanal in camellia oil (oleic acid mainly) increased significantly, and correlated linearly with TOTOX (21.6 TOTOX - 595, R(2) = 0.92); propanal increased significantly in perilla oil (linolenic acid mainly) and correlated linearly with TOTOX (8.10 TOTOX + 75.0, R(2) = 0.90). Hexanal (9.56 TOTOX + 913, R(2) = 0.90, and 7.10 TOTOX + 342, R(2) = 0.78, respectively) and nonenal (10.5 TOTOX + 691, R(2) = 0.95, and 6.65 TOTOX + 276, R(2) = 0.84, respectively) in sunflower oil (linoleic acid mainly) and palm oil (palmitic and oleic acids mainly) also had good linear correlations with TOTOX. Considering the change patterns of these four aldehydes, it was found that the oxidation stability was in the order sunflower oil < camellia oil < perilla oil < palm oil, which was same as POV, TOTOX, and total nonpolar carbonyls. It was concluded that the four aldehydes nonanal, propanal, hexanal, and nonenal could be used as oxidation indicators for the four types of oils.