Effects of extraction solvents, cooking procedures and storage conditions on the contents of ergothioneine and phenolic compounds and antioxidative capacity of the cultivated mushroom Flammulina velutipes

Edible mushrooms contain considerable amounts of the potent natural antioxidant 2-thiol-l-histidine-betaine (l-ergothioneine, ESH). The objective of this study was to evaluate the effects of extraction solvents, common cooking methods and storage conditions on the ESH content, total phenols (TPs) and antioxidant capacity of the edible mushroom Flammulina velutipes fruiting body and its hot water extract that had been stored at different temperatures. Regarding cooking procedures, boiling in water resulted in the highest losses of antioxidant activity of both ESH and TPs. Most of the losses of ESH and TPs were detected in the cooking water. The ESH contents in the raw mushroom fruiting bodies significantly decreased after 8 days of refrigerated storage under both dark and fluorescent lighting conditions. However, the TP content in the raw mushroom stored under fluorescent lighting significantly increased during 10 days of refrigeration. In contrast, the ESH and TP contents as well as DPPH radical scavenging ability of the fruiting bodies remained unchanged for up to 15 days of frozen storage at -18 degrees C. The same behaviour was obtained with the mushroom extract packed in plastic tubes. The correlation between DPPH radical scavenging activity and ESH contents was higher than that for TP compounds.