Influences of CO₂ and 0₂ on the Keeping Freshness of Shii-take (Lentinus edodes(Berk)Sing.) after Harvest

Abstract

This study was conducted to investigate the effect of CO₂ and 0₂ on keeping freshness of shii-take (Lentinus edodes(Berk)Sing.) under the controlled aptmoshere (CA) storage. The level of 0₂ below 2% markedly suppressed browning of the gill, polyphenol oxidase (PPO) activity and an increase of free amino acid content in shii-take. On the other hand, regardless of its levels, CO₂ strongly inhibited PPO activity and the increase of free amino acid content during storage. But under this condition fermentation took place and off-flavor was generated after 2 days at 20°C. The higher concentration of CO₂, the stronger off-flavor. Some volatiles, especially formaldehyde and ethyl alcohol increased in 100% CO₂ storage of shii-take. On exposure to air, these components decreased gradually and were not detected any more after 6 hr. At this time, browning of the gill was not observed and shelf life of shii-take was maintained. Above these results, it was found that the best condition of controlled atmosphere for keeping freshness of shii-take was at 40% CO₂ and 1-2% 0₂, and by this treatment, shelf life of shii-take could be extended 4 times at 20°C as long as that of non-treated one.