Study of Phenol Oxidases on Browning of Shiitake (Lentinus edodes Sing.) Mushroom

Abstract

It has been known that phenol oxidase (monophenol oxidase, o-diphenol oxidase and laccase) activities in shiitake mushroom were inhibited by internal and external ethyl alcohol. In this paper, proteins from shiitake were separated by gel electrophoresis and stained with CBB or phenolic substrates. Monophenol oxidase, o-diphenol oxidase and laccase were detected four different isozymes each at the same Rms, and their activity changes occurred during browning of shiitake. The enzyme bands of browned shiitake packaged in perforated polyethylene bags were thicker and larger than those of shiitake packaged in airtight polyethylene bags. The inhibition of phenol oxidase activities was also observed on the enzyme bands of shiitake exposed to ethyl alcohol vapor during storage. When the slices of shiitake were treated with an inhibitor of protein synthesis (cycloheximide 0.1mM), browning and o-diphenol oxidase activity in the slices were definitely inhibited. From these results, it was considered that ethyl alcohol was produced in the tissue of shiitake under an anaerobic atmosphere, and then it affected synthesis of phenol oxidases, therefore browning of shiitake was inhibited.