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A thorough insight into the complex effect of gamma-tocopherol on the oxidation process of soybean oil by means of 1H Nuclear Magnetic Resonance. Comparison with alpha-tocopherol

Martin-Rubio, A.S., Sopelana, P., Guillén, María D.
Food research international 2018 v.114 pp. 230-239
alcohols, aldehydes, alpha-tocopherol, epoxides, gamma-tocopherol, hydroperoxides, moieties, nuclear magnetic resonance spectroscopy, oxidation, soybean oil
The effect of γ-tocopherol in proportions between 0.02 and 2% by weight on the accelerated storage process of refined soybean oil is studied by 1H NMR, and compared with that of α-tocopherol. Whereas the lowest γ-tocopherol enrichment level does not affect oil evolution, at higher concentrations both γ- and α-tocopherols initially accelerate acyl groups degradation and hydroperoxides generation, more as higher is the tocopherol concentration, this effect being less marked for γ-tocopherol. However, after this initial stage, the rates of acyl groups degradation and hydroperoxides formation decrease with tocopherol concentration. Furthermore, in the case of γ-tocopherol, the higher the enrichment degree, the later hydroperoxides decomposition occurs, so that, unlike α-tocopherol, γ-tocopherol delays the generation of most secondary oxidation products (aldehydes, (E,E)-keto-dienes, epoxy-keto-enes, (E)-epoxystearates and alcohols) with the exception of some epoxides. Similarly to α-tocopherol, γ-tocopherol modifies the oil oxidation pathway at the highest addition level, promoting the formation of compounds with (Z,E)-isomerism, although less noticeably than α-tocopherol.