Effects of Gamma-irradiation on Fatty Acids and Oxidative Stability of Oil from Treated Walnuts. Impact of Antioxidant Compositions on Oil Autoxidation

Gamma-irradiation at doses of 10 kGy and 25 kGy was applied on walnuts in order to study changes in the fat yield, fatty acids composition, conjugated dienes and trienes, tocopherols and oxidative stability of the extracted glyceride oils. The results revealed no significant changes in fat yield and fatty acids composition but an increase of dienes and trienes, and a decrease in tocopherols amount. Decrease of Induction periods of oils autoxidated at 80 ⁰C, 100 ⁰C, and 120 ⁰C was observed as well. In order to reduce the negative effects of radiation-related lipid oxidation walnut oils were supplemented with binary antioxidant mixtures. Thus, the composition of ascorbyl palmitate and α-tocopherol in 2:1 ratio slightly prolonged the induction periods while halving of the initial oxidation rate of oils extracted from irradiated walnuts at the same time.