Effect of Fatty Acid and Tocopherol on Oxidative Stability of Vegetable Oils with Limited Air

Oxidative stabilities represented with variance of fatty acids, tocopherols, acid value, peroxide value, and thiobarbituric acid value of edible vegetable oils with limited air were investigated. The total tocopherol contents were positively correlated with the polyunsaturated fatty acids (PUFA, r(2) = 0.856), negatively correlated with the monounsaturated fatty acids (MUFA, r(2) = -0.598), and saturated fatty acids (SFA, r(2) = -0.258) in initial oxidation. The residual contents of tocopherols had good negative linear correlations with the peroxide value and thiobarbituric acid value during oxidation. When alpha-tocopherol predominated over other homologue, it presented a pro-oxidant effect at high concentration, but would transform to be an antioxidant as its concentration decreased to the inflection point that corresponded to the inflection point of peroxide value increase for different kinds of vegetable oils. However, the gamma- or delta-tocopherol did not show pro-oxidant action. Therefore, the influence of alpha-tocopherol on oxidation was likely more predominant than fatty acids were.