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

Lampi, Anna-Maija, Hopia, Anu, Piironen, Vieno
journal of the American Oil Chemists' Society 1997 v.74 no.5 pp. 549-555
antioxidant activity, butter oil, oxidation, peroxide value, tocopherols, triacylglycerols
The 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.