presents data on the content of vitamin D2 in sliced fresh button mushroom subjected to UVB irradiation for a period of 5–
30 min. In addition for comparison, whole mushrooms with gills facing (closed fruit bodies) were irradiated with UVB for 30 min. It can be seen from the data in Fig. 1 that the prolonged irradiation with UVB does not increase ergocalciferol content in fresh button mushrooms.