Gamma-and delta-tocopherols are more effective than alpha-tocopherol on the autoxidation of a 10% rapeseed oil triacylglycerol-in-water emulsin with and without a radical initiator

摘要

The antioxidative effects of gamma- adn mainly delta-tocopherol in a multiphase system were hardly considered up to now.the aim of this study was i)to assess the effects and ii)to follow the degradation of alpha-,gamma- and delta-tocopherol in concentrations of 0.01%,0.05%,0.1% and 0.25% during the oxidation of a 10% purified rapessed oil triacyl glycerol-in-water emulsin at 40 deg C in te dark for 15 wk in a system containing a low oxygen concentation.Oxidatin experments were performed weekly by assessing the formation of hydroperoxides and hexanal,and the stability of the tocopherols was determined using high-performance liquid chromatography.Storage tests were conducted wtih adn without the addition of 0.01% alpha,alpha'-azoisobutyronitrille (AIBN),which is a known radical initiator.alpha-Tocopherol increased the formatin of hydroperoxides in both tests as well as the generation of hexanal when the redical initiator was added;furthermore it was the least stable.gamma-Tocopherol delayed the formation of hexanal and prolonged the stabilityof the emulsin in a dose-dependent manner.delta-Tocopherol was the most atable and also the most effective in delaying lipid oxidatin in the emulsions.Each concentration that was tested reduced the rate of hydroperoxide adn especially hexanal formatin.Hexanal was only formed to a slight extent after 15 wk of oxidatin in the test with AIBN and the lowest dose of 0.01% delta-tocopherol.For all tocopherols,strong orrelatins were found between tocopherol stability and the extent of oxidation.results suggest that i)mainly delta-tocopherol,but also gamma-tocopherol even less pronounced,are very good antioxidants in order to stabilize and prolong the shelf life of oil-in-water emulsions,ii)the antioxidative effects were intensified with increasing amounts.