Escalating Vitamin D2 Content in Fresh Sporocarps of Elm Oyster Mushroom Hypsizygus ulmarius (Bull.) Redhead (Agaricomycetes) Using Ultraviolet Irradiation and Assessment of Its Stability, Antioxidant Capacity, Color, and Textural Properties

Mushrooms are widely recognized as a superfood, being the only natural source of vitamin D₂, which makes them a valuable dietary food. Their popularity is rapidly increasing in the current era of heightened health awareness. The present study examined the effect of UV-B and UV-C irradiation on the vitamin D₂ content, its stability, antioxidant capacity, color, and textural properties of Hypsizygus ulmarius. The results revealed that the initial vitamin D₂ concentration in untreated samples was 74.82 ± 0.09 μg/100 g dw. After 90 min of UV-B exposure, the vitamin D₂ content peaked at 6813.39 ± 0.04 μg/100 g dw. However, UV-C irradiation first led to a rise in vitamin D₂ levels, reaching their highest point (388.30 ± 0.01 μg/100 g dw) after 45 min, followed by their subsequent decline. Stability analysis showed that freeze-dried mushroom powder retained more vitamin D₂ than fresh sporocarps after 7 days of storage at 4 °C. The UV-B treatment significantly enhanced antioxidant properties, increasing TAA (35.84%), DPPH (17.77%), ABTS (11.57%), and FRAP (18.36%) values. The color and texture of the samples also changed post-irradiation, with notable increases in hardness, springiness, cohesiveness, and color intensity, alongside a decrease in whiteness. The study concluded that UV-B irradiation effectively boosts the vitamin D₂ content and antioxidant capacity of H. ulmarius besides inducing some alterations in its optical and textural properties.