Effect of Co-60 gamma irradiation on Aspergillus flavus, Aflatoxin B1 and qualitative characteristics of pistachio nuts (Pistacia vera L.)

In this study the effect of different doses of gamma irradiation (0, 0.5, 1, 1.5, 2, 4 and 6 kGy) on viable spore population of Aspergillus flavus, Aflatoxin B-1 (AFB(1)) concentration and qualitative characteristics of pistachio samples were investigated. The results indicated that gamma irradiation at doses of 4 and 6 kGy reduced the viable spore population of A. flavus about 5 log. The maximum degradation of AFB(1) in pistachio samples was 73.26% and 83.36% that was observed at doses of 4 and 6 kGy, respectively. The total phenol content (TPC) increased at dose of 2 kGy, but it was reduced at higher doses of irradiation. The increase of irradiation doses up to 4 kGy significantly increased the antioxidant activity, while irradiation dose of 6 kGy led to a reduction in antioxidant activity. All irradiation doses increased the amount of malondialdehyde in pistachio samples and the highest amount of malondialdehyde was observed at dose of 6 kGy. The chlorophyll and carotenoid content was decreased at all absorbed doses of gamma irradiation and affected the color features and resulted to a darker color of pistachio samples. Gamma irradiation slightly decreased the solubility of proteins and altered the pattern and intensity of the protein bands. The obtained results showed that gamma irradiation at doses higher than 2 kGy is capable of controlling and reducing the contamination of pistachio samples, while lower doses (kGy <= 2) of gamma irradiation caused minimum changes in pistachio samples quality.