Evaluating the Effect of Gamma Radiation on the Total Phenolic Content, Flavonoids, and Antioxidant Activity of Dried Pleurotus ostreatus ((Jacq. ex. Fr) Kummer) Stored in Packaging Materials

Dried Pleurotus ostreatus mushrooms stored in polythene and polypropylene packs were exposed to gamma radiation from a cobalt-60 source at doses of 0, 0.5, 1, 1.5, and 2 kGy at a dose rate of 1.7 kGy/hr and stored for a period of 1 month. Total phenolic contents, flavonoids, and free radical scavenging activity DPPH (2,2′-diphenyl-1-picrylhydrazyl) were determined using aqueous, ethanol, and methanol extracts by Folin-Ciocaultaeu method as a source of potential natural antioxidants. Total phenol content ranged 0.56 ± 0.01–10.96 ± 1.7 mg/GAE, flavonoids ranged 1.64 ± 0.05–8.92 ± 0.6 mg/QE, DPPH radical scavenging activity also ranged 7.02 ± 0.10–13.03 ± 0.04%, and IC50 values also ranged 0.08–0.16 mg/mL. Statistical differences (P < 0.05) were recorded for the extracts and the treatment doses of mushrooms stored in polythene and polypropylene packs. A significant linear correlation was confirmed between values for the total phenolic content and antioxidant activity of mushroom extracts. The high contents of phenolic compounds indicated that these compounds contribute to high antioxidant activity. Pleurotus ostreatus can be regarded as a promising candidate for natural mushroom sources of antioxidants with high value. The use of low dose gamma radiation by the local food industry could improve the hygienic quality, extend shelf-life, and preserve nutrients and antinutrients.