Temperature stability of vitamin D2 and color changes during drying of UVB-treated mushrooms

Abstract

ABSTRACTThe study investigates the effect of drying temperature on vitamin D2 content and color changes of UVB-treated shiitake (Lentinula edodes), oyster (Pleurotus ostreatus), and white and brown button mushrooms (Agaricus bisporus). Fresh samples were UVB treated up to 1.5 J/cm2 for 20 min at 25°C and either dried in a high precision dryer (temperatures: 40, 60, 80°C, specific humidity: 10 g/kg, air velocity: 0.6 m/s) or frozen at −25°C, and then freeze-dried (pressure: 0.28 mbar). Vitamin D2 content was not negatively affected by the increased temperatures of the drying air. The highest content of vitamin D2 was detected in freeze-dried (171.84 µg/g) and hot-air dried shiitake at 60°C (169 µg/g), followed by oyster (121.96 µg/g), whereas the lowest amount was observed in brown button mushrooms at 40°C (34.65 µg/g). Although vitamin D2 indicated a remarkable stability even at 80°C, the dried samples were characterized by intensive tissue darkening.