Lipid oxidation, expressed as malondialdehyde (MDA) content of oil extracted from control samples of pistachio (0.023 mg
MDA/kg oil), was lower than those of oil extracted from samples treated with 1 kGy or 3 kGy (0.025 mg MDA/kg oil) (Table 3). The TBA values decreased significantly in both irradiated and non-irradiated samples, showing significant differences among irradiated and non-irradiated samples within the 12 months of storage. These results are in agreement with those of Wilson-Kakashita, Gerdes, and Hall (1995) who observed no differences in TBA values for walnuts
after irradiation with doses up to 20 kGy. The slight increase in TBA value for oil extracted from irradiated pistachio was due to the fact that auto-oxidation of fat is accelerated by the free radicals produced during irradiation to form hydroperoxides, which break down into various decomposition products, including aldehydes, of which malonaldehyde is the major TBA-reactive substance (Hoyland & Taylor, 1991).