Effects of UV Light on Mechanical Properties and Production of Vitamin D2 in Mushrooms

Abstract

The sun emits ultraviolet radiation in form of ultraviolet-A (UV-A), ultraviolet-B (UV-B), and ultraviolet-C (UV-C) bands. Ultraviolet light may boost vitamin D2 production in mushrooms which human bodies cannot synthesize. The ergosterol in mushrooms, a component of fungal cell membranes which serves the same function as cholesterol in animal cells, can be converted into vitamin D2 by ultraviolet light. However, mushrooms are conventionally grown in the dark, necessitating artificial ultraviolet irradiation. This study investigated the effects of UV-A and UV-C light on concentration of vitamin D2 in oyster mushrooms during growth and mechanical properties post-harvest. UV exposure times were varied from 10 to 60 minutes per day at intervals of 10 minutes, and irradiation done for three days. UV spectroscopy was used to determine the amounts of Vitamin D2 and the mechanical properties were investigated using dynamic mechanical analysis (DMA 2980). Absorbance of vitamin D2 for UV-A light ranged from 0.18 to 0.49 for 10 to 60 minutes of irradiation, respectively, while for UV-C light the vitamin D2 content absorbance was 0.38 to 0.81 for 10 to 60 minutes of irradiation, respectively. The storage modulus, loss modulus, and loss factor of the irradiated samples and control samples were determined for both UV bands. UV-C light irradiated samples had higher loss modulus and loss factor, but low storage modulus as temperature increased from 35-100oC with respect to the control sample, while UV-A light irradiated samples had lower loss modulus, low loss factor, and higher storage modulus than UV-C irradiated samples. Thus, oyster mushrooms with a well-defined content of vitamin D2 can be obtained without largely affecting the mechanical properties and the quality of the mushrooms.