Impact of Pre-drying Treatments on Antioxidant Activities and Quality of Dried Golden Oyster Mushroom (Pleurotus citrinopileatus)

The effects of three pre-drying treatments including blanching in hot water (60^oC-70^oC for 3 and 5 min), soaking in NaCl (1-4% w/v for 10 and 20 min), and soaking in citric acid (0.2-0.8% w/v for 10 and 20 min) on dried Golden oyster mushroom (GOM) were studied. Color values (L*, a*, and b*), browning index (BI), polyphenol oxidase (PPO) activity, protein content, flavonoid content (FC), total phenolic content (TPC), and antioxidant activities (metal chelating activity and DPPH radical scavenging activity) of dried mushrooms were evaluated. All pretreated mushrooms had significantly higher lightness (L*) and lower a* and b* values compared to those of un-pretreated ones. Decreases in BI and PPO activity were observed in pretreated mushrooms. Higher blanching temperatures, concentrations of NaCl and citric acid, and time yielded lower protein content, TPC, and FC. Among the pretreatments, the highest antioxidant activities were observed in citric acid treated GOM. Thus, blanching and chemical pretreatments could enhance the lightness and lower BI of dried GOM, although they lowered the nutrient levels and antioxidant activities of the dried GOM.