Vitamin D2 enrichment in mushrooms by natural or artificial UV-light during drying

This paper investigates the effect of direct sunlight during natural sun drying and solar drying in a forced convection type solar dryer on vitamin D 2 content of brown button mushrooms ( Agaricus bisporus ). Commercial UVB light, sample processing and drying methods on vitamin D 2 content were also studied via different UVB-drying strategies. Mushrooms of the same flush were divided in different groups: i) slices were dried under the sun and in an innovative solar dryer, ii) slices were UVB-treated and dried either by freeze- or convective drying, iii) whole fruit bodies were UVB-treated, sliced and freeze-dried, iv) freeze dried samples were UVB-treated in the form of slices or powder. UVB-treatment of whole mushrooms led to remarkable vitamin D 2 enrichment (45 μg/g dry matter), while slicing of mushrooms prior to UVB exposure resulted in a ten-fold increase in D 2 content (406 μg/g). UVB light exposure of already dried slices and powder also induced high vitamin D 2 generation. Sun-dried and solar-dried mushrooms contained 36 and 39 μg/g dry matter vitamin D 2 , respectively. Although commercial UVB light boost D 2 synthesis in mushrooms, solar drying represents a viable method for the natural formation of ergocalciferol in mushrooms and an excellent vitamin D source for vegans.