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 1h. 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.