Effect of gamma irradiation on total phenolic content yield and antioxidant capacity of Almond skin extracts

Almond (Prunus amygdalus) skins are agricultural by-products that are a source of phenolic compounds. Phenolic compounds from gamma-irradiated almond skins were extracted with 40% ethanol. Total phenolic content was determined using the Folin–Ciocalteu (F–C) method. Almond skin extracts (ASE): soybean oil (1:4 v/v) mixtures containing 0.08% FeCl3 were prepared. Antioxidant activity was determined by conjugated dienes and trienes (CD and CT, respectively) measurements, peroxide value (PV), Trolox® equivalent antioxidant capacity (TEAC) and Photochemiluminescence (PCL). Phenolic content yield (p < 0.05) was higher in ASE irradiated at doses greater than 4 kGy (trial I) or 12.7 kGy (trial II) compared to the control. Increased antioxidant activity was observed in TEAC assay and PCL with lipid-soluble antioxidant capacity reagents in ASE irradiated above 4 kGy (trial I) and 12.7 kGy (trial II) compared to 0 kGy. Gamma irradiation of almond skins thus increased the yield of total phenolic content as well as enhanced antioxidant activity of extracts.