| Abstract
| - Controversial data on the antioxidant effects of tocopherols have already been shown in differenttest systems, yet δ-tocopherol was hardly considered. This study was designed to assess the effectsand degradation of α-, γ-, and δ-tocopherol in four concentrations from between 0.01 and 0.25% onthe oxidation of purified rapeseed oil trigacylglycerols (RO-TAG) at 40 °C in the dark in a low oxygencontaining system for 11 weeks. Oxidation experiments were performed weekly by assessing primary(peroxide value, PV; conjugated dienes, CD) and secondary (p-anisidine reactive products, p-AV;hexanal) oxidation products, the degree of unsaturation with the iodine value (IV), and the stability oftocopherols. Test approaches were performed with and without the addition of 0.01% α,α‘-azoisobutyronitrile (AIBN), which is a known radical initiator. α- and γ-Tocopherols increased therate of lipid oxidation, which was more pronounced in the presence of AIBN. Only the lowest amountof 0.01% γ-tocopherol was comparable to the control sample in the test without AIBN. The mosteffective was shown to be δ-tocopherol, which did not elevate lipid oxidation except the PV in theAIBN test, but they did not delay it either. δ-Tocopherol was the most stable followed by γ- andα-tocopherol. For α- and γ-tocopherol, but not for δ-tocopherol, strong correlations were found betweenthe tocopherol degradation and the extent of oxidation. Results suggest that (i) at concentrationshigher than 0.05%, tocopherols are less efficient and turn their mode of action or participate in sidereactions in RO-TAG and (ii) δ-tocopherol was shown to be the most stable and effective underthese low oxygen conditions. Keywords: α-, γ-, δ-Initiator; lipid oil; oxidation; primary products; radical; rapeseed
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