Abstract
It is well known that ergosterol (provitamin D2) transforms to vitamin D2 by ultraviolet light irradiation. We studied efficient transformation of ergosterol to vitamin D2 in the materials (shiitake (Lentinus edodes), enokitake (Flammulina velutipes), hiratake (Pleuntus ostreatus), bakers' yeast, beer yeast and koji mold). Each powdered material was irradiated by ultraviolet light under vibration conditions. It was confirmed that a portion of ergosterol in all the materials was transformed vitamin D2 by the treatment mentioned above. Yield of vitamin D2 increased over 1000IU/g in every material for only 3 minutes. Yield of vitamin D2 tends to increase with high contents of ergosterol. Yields of vitamin D2 in shiitake under vibration conditions increased linearly up to 10 minutes and reached 10000IU/g. On the other hand, yield of vitamin D2 in shiitake under stationary conditions was 2500 IU/g for 10 minutes. Transformation efficiency between the two was 4-fold. Thermostability of vitamin D2 in shiitake was equal to that of vitamin D2 in cellulose powder. Storage stability was superior to the control. It was thought that these fortified materials were of great value as additives in the field of food, petfood and feed
