Enhancement of vitamin D-2 in edible mushroom using ultraviolet irradiation and assessing its storage and cooking stability

Purpose The purpose of this study was to optimize the parameters for enhancing the vitamin D-2 formation in three edible mushroom varieties, namely, shiitake mushroom (Lentinula edodes), white button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus) using ultraviolet (UV) irradiation. Design/methodology/approach Freshly harvested mushrooms were irradiated with UV-B and UV-C lamps. Further, mushrooms were treated with UV-B at a distance ranging between 10 and 50 cm from the UV light source, for 15-150 min, to maximize the conversion of ergosterol to vitamin D-2. Analysis of vitamin D-2 content in mushrooms before and after UV exposure was done by high pressure liquid chromatography (HPLC). Findings HPLC results showed a significant (p < 0.001) increase in vitamin D-2 levels of shiitake (17.3 +/- 0.35 mu g/g), button (24.9 +/- 0.71 mu g/g) and oyster (19.1 +/- 0.35 mu g/g) mushrooms, irradiated with UV-B at a distance of 20-30 cm for 120 min. Further, stability studies revealed that vitamin D-2 levels in UV-B-irradiated mushrooms gradually increased for 48 and 72 h of storage at room and refrigeration temperatures, respectively. During cooking operations, 62%-93% of vitamin D-2 was retained in UV-B-irradiated mushrooms. Originality/value This study describes the most effective parameters such as ideal wavelength, mushrooms size, duration of exposure and distance from UV sources for maximum vitamin D-2 formation in edible mushrooms using UV irradiation. Further, assessment of vitamin D-2 stability in UV exposed mushrooms during storage period and cooking operations has been carried out. In addition, this study also provides a comparison of the vitamin D-2 levels of the three widely cultivated and consumed mushroom varieties treated simultaneously under similar UV exposure conditions.