Effect of ultraviolet‐ B irradiation on antioxidative properties of aqueous extracts from shiitake ( L entinus edodes ) mushrooms

Summary Antioxidant properties of aqueous extracts from L entinus edodes treated with UV ‐ B irradiation were examined in vitro systems including DPPH , ABTS and oxygen radical absorbance capacity ( ORAC ) assays and in riboflavin‐photosensitised oil‐in‐water ( O / W ) emulsions. Changes in total phenolics, total flavonoids and vitamin C were also analysed. Lentinus edodes receiving 25 kJ m −2 UV ‐ B treatment showed high radical scavenging ability based on DPPH and ABTS assays compared with samples with 0, 50 and 75 kJ m −2 , while those with 50 kJ m −2 had higher antioxidant capacities than other samples from ORAC assays. Samples with 25 kJ m −2 UV treatment had significantly 7.1% higher total phenolic content, 12.0% higher total flavonoid content and 8.0% higher vitamin C content than UV ‐ B ‐untreated sample ( P  <   0.05), respectively. In O / W emulsions under riboflavin photosensitisation, 25 and 50 kJ m −2 UV treatment significantly increased the oxidative stability compared with other samples based on headspace oxygen content and lipid hydroperoxide analyses ( P  <   0.05). Aqueous extracts of UV ‐ B ‐treated mushrooms possessed enhanced antioxidant properties compared with untreated mushrooms.