Antioxidant Effects of Endogenous Components in Vegetable Oils

Different endogenous components (tocopherols, phytosterols, polyphenols and squalene) of vegetable oils were added to compounded vegetable oils to investigate the antioxidant effects. Using a Schaal oven-accelerated experiment, the effects of endogenous antioxidants on the oxidative stability of compounded oils were examined by changes of fatty acid composition, acid value, peroxide value, anisidine value, and total oxidative value. The results demonstrated that the individual tocopherols and polyphenols showed a substantial antioxidant impact, and the antioxidant effect increased with concentration. As the concentrations of tocopherols and squalene increased, the combined of tocopherols and squalene showed antagonistic antioxidant effects and then synergistic effects, and the presence of squalene significantly increased the antioxidant capacity of tocopherols when the tocopherol content was greater than 480 mg/kg (P<0.05). The fatty acid composition of the compound oil without pretreatment to remove the antioxidant components changed only marginally as a result of accelerated oxidation, whereas the fatty acid content of the pretreated compound oil changed significantly. The degree of change in acid value and total oxidative value before and after oxidation was likewise much greater in pretreated compound oils than those in untreated compound oils (P<0.05). The addition of tocopherols and polyphenols increased the oxidative stability of the compound oils, demonstrating that the concentration of endogenous antioxidant components, while minor, played an important role in delaying the oxidation process of vegetable oils. Tocopherols, phytosterols, polyphenols, and squalene were the key endogenous components in vegetable oils, with tocopherols and polyphenols playing important antioxidant roles and complicated interactions between the endogenous components. The findings of this study can be used to guide the use of endogenous antioxidant components to increase the oxidative stability of vegetable oils.