Enhancement of Antioxidant Properties and Increase of Content of Vitamin D2 and Non-volatile Components in Fresh Button Mushroom, Agaricus bisporus (Higher Basidiomycetes) by γ-irradiation

Agaricus bisporus is a popular culinary-medicinal mushroom in Taiwan, and γ-irradiation could extend its shelf life. Our objective was to study the content of vitamin D2 and the taste components and antioxidant properties of ethanolic extracts from A. bisporus with various doses of γ-irradiation. After irradiation, the vitamin D2 content of 5-10 kGy irradiated mushrooms was in the range of 5.22-7.90 µg/g, higher than that of the unirradiated control (2.24 µg/g). For all treatments, the total content of soluble sugars and polyols ranged from 113 to 142 mg/g, and the monosodium glutamate-like components ranged from 6.57 to 13.50 mg/g, among which the 2.5 kGy irradiated sample has the highest content of flavor 5'-nucleotide. About antioxidant properties, 10 kGy irradiated samples exhibited lower EC50 values than did other samples. EC50 values were less than 5 mg/mL for ethanolic extracts. Total phenols were the major antioxidant components and the total content was 13.24-22.78 mg gallic acid equivalents/g. Based on the results obtained, γ-irradiation could be used to improve the vitamin D2 content and intensity of umami taste in fresh mushrooms. In addition, γ-irradiation not only maintained the antioxidant properties of mushrooms but also enhanced the antioxidant properties to some extent.