Antioxidant activity of minor amounts of γ‐tocopherol in natural triacylglycerols

Abstract

AbstractThe effects of minor amounts of γ‐tocopherol on the oxidation of natural triacylglycerols (TAG) of rapeseed (RO) and butter oils (BO) were studied. Four different TAG materials were blended from chromatographically purified TAG that contained 100–25% of RO TAG. The RO TAG contained from <1 to 43 µg γ‐tocopherol per gram of TAG, which corresponded to ≤6% of the total tocopherols in the original RO. The TAG were held at 40°C in the dark for 4 wk and followed at regular intervals by measurements of hydroperoxide formation by peroxide values and of secondary product formation by p‐anisidine values at regular intervals. In all TAG, minor amounts of γ‐tocopherol retarded oxidation. In RO TAG, concentrations as low as 11 µg/g of γ‐tocopherol (1.5% of the total tocopherols in the original RO) were enough to decrease hydroperoxide and secondary product formation to 46 and 39%, respectively. The effect was even more important in TAG mixtures that contained BO TAG. There were no significant differences between oxidation of the RO TAG at 24 µg/g, the 75% RO TAG mixture at 11 µg/g, and the 50% RO TAG mixture at 3 µg/g of γ‐tocopherol. Even at these minor levels, γ‐tocopherol was a significant antioxidant, which is important in oxidation studies of purified model systems.