Abstract
Effect of solar radiation on vitamin D_2 contents in raw and dried Shiitake mushrooms (Lentinus edodes) was investigated. Contents of vitamin D_2 in raw Shiitake cultured in vinylhouses (average : 21 and 14 IU/piece) were generally lower than those cultured outdoors (average : 100 IU/piece). On the other hand, the contents of ergosterol in all the samples were much higher than those of vitamin D_2 (about 9,000〜46,000 times as weight ratio). When gills parts of the samples cultured in a vinylhouse were exposed to sunlight for 1 h or 3 h at a fine day, the contents of vitamin D_2 increased about 3.6 times (average : 76 IU/piece) or 5 times (average : 104 IU/piece) higher than those before radiation (average : 21 IU/piece). The vitamin D_2 contents in raw Shiitake increased according to increase of solar radiation times. When gills parts of dried Shiitake were exposed to sunlight for 1 h or 3 h, the contents of vitamin D_2 increased about 24 times (average 488 IU_piece) or 27 times (average : 548 IU/piece) higher than those before radiation (average : 20 IU/piece). The contents of vitamin D_2 in raw and dried Shiitake exposed on gills part were significantly higher than those in the samples exposed on pileus parts. Since no significant change was observed in the smell, color and taste of Shiitake by solar radiation, exposure to sunlight is an effective method for increase of vitamin D_2 in raw Shiitake mushurooms.
