Antioxidative Capacity Of α-tocopherol In Corn Oil, Soybean Oil And Camellia Seed Oil

During the storage of edible oil, the oxidation of oil is a common phenomenon. The most common method that to slow down the oxidation of edible oil is to add artificial antioxidants into edible oil, but artificial antioxidants are of the carcinogenic and other shortcomings, so the apply of non-toxic, natural antioxidants has became an inevitable trend in edible oil industry. α-Tocopherol is the non-toxic natural antioxidants presenting in plant oils. The most research about the antioxidant effect of α-tocopherol was adding different concentrations of α-tocopherol into oil, through the difference concentration of the primary and secondary products in lipid oxidation to explore the antioxidant activity of α-tocopherol, there is no article that from the perspective of fat oxidation kinetics to study the antioxidant effect of α- tocopherol in edible oil. According to the mechanism of lipid oxidation and antioxidants, the present study established the Arrhenius kinetic model of α-tocopherol in the oil,the kinetic not only helps to explain antioxidant mechanisms of α-tocopherol in oxidation process of edible oil but also has some significance guide in the daily production of edible oil.The main research contents and results:1. There are some antioxidants like tocopherol and synthe tic antioxidants in commercial corn oil, soybean oil and camellia oil, as well as some promoting oxidation substance of lipid like free fatty acids, peroxides and trace metal presence in oil. Thus, these presence substance in oil have adverse effects on the study of α-tocopherol antioxidant activity, so it is need that corn oil, soybean oil and camellia oil to be purified to remove these substance, to be better to explore the antioxidant effect of α-tocopherol.2. The oxidative kinetic study of purified corn oil, soybean oil, and camellia seed oil with adding 50 ppm、100 ppm、200 ppm and 400 ppm of α-tocopherol stored at 40 ℃、60 ℃and 75 ℃was investigated. The increase of peroxide values, p-anisidne values and total oxidation value were determined with prolonging oxidation periods, which indicated the antioxidant efficiency of α-tocopherol growing with the concentrations of α-tocopherol increasing when the concentrations of α-tocopherol below the optimum concentration. On the contrary, the antioxidant efficiency of α-tocopherol is weakening even take an prooxidation effect with increasing the concentrations of α-tocopherol increasing when the concentrations of α-tocopherol is higher than the optimum concentration.3. The regression coefficients were obtained from fitting equation for the peroxide value、anisidine value and total oxidation value with oxidation time, which indicated the oxidation kinetics of corn oil, soybean oil and camellia seed oil followed a zero-order or first-order kinetic. In this case, the oxidation rate of primary product could substitute the oxidation rate of oil, whereby the oxidation rate of oil with different concentrations of α-tocopherol could be obtained. The oil oxidation rate is affected of not only the added concentrations of α-tocopherol, but also the temperature of accelerating oxidation, then the oxidation rate constant of lipid with temperature is in line with Arrhenius equation model: The higher the temperature of the oil to oxidation, the greater oxidation rate of oil is obtained; the temperature of oil accelerate oxidation changes, the added optimum antioxidant concentrations of α-tocopherol in oil also changes.