Dynamics of sterols and fatty acids during UV-B treatment of oyster mushroom

Fruiting bodies of the oyster mushroom Pleurotus ostreatus were illuminated with UV-B with a light intensity maximum at 310–320 nm and 11.5 W/m2 for 60 min at 20 °C. Changes of the sterol and fatty acid spectrum were quantified. The onset of ergocalciferol (vitamin D2) formation was immediate in fruiting bodies illuminated from the lamella side, in sliced fruiting bodies, and in the stipes. Saturation concentrations above 100 μg/g of dry matter were reached after 1 h. At the same time, the concentrations of the photo-isomers lumisterol2, tachysterol2 and previtamin D2 increased in this order. 22-Dihydroergocalciferol (vitamin D4), showed the same course of increase and reached a maximum concentration of around 20 μg/g dry matter. With the exception of linoleic acid in cut fruiting bodies, fatty acid concentrations remained almost constant. One serving of UV-B pretreated sliced oyster mushroom covered the weekly demand of vitamin D of an adult.