The results in Table 3 indicated that immediately after irradiation, all doses of gamma irradiation significantly (p < 0.05)
decreased the free fatty acids in pistachio oils. After 12 months of storage, the free fatty acid concentrations of oil extracted from pistachio nut treated with 1, 2 and 3 kGy were significantly higher than in the control. On the contrary, Abd El-Aziz and Abd El-Kalek (2011) have reported that free fatty acids in pumpkin seeds and pumpkin oil increased with increasing the irradiation dose (1–10 kGy). However, the changes in free fatty acids were not significant, and the changes in irradiated oil were higher than irradiated seeds. The effects of gamma irradiation on irradiated oil appear with the radiation dose 3 kGy and abouve.