EFFECTS OF WASHING ON POLYPHENOLS AND POLYPHENOL OXIDASE IN COMMERCIAL MUSHROOMS (AGARICUS-BISPORUS)

To explain differences in browning of skin tissue between unwashed and washed mushrooms, changes in soluble phenols, major substrates of pol yphenol oxidase (PPO), and PPO isozymes during washing, as well as eff ects of sodium hpochlorite (NaOCl) on phenolic compounds in mushrooms were investigated. About 15% of the soluble phenols from the skin of m ushroms, mostly gamma-L-glutaminyl-4-hydroxybenzene (GHB) and gamma-L- glutaminly-3,4-dihydroxybenzene (GDHB), were leached out during washin g. Among four isozymes of partially purified PPO separated by native e lectrohoresis, the two faster migrating forms were leached out during washing. Phenolic compounds extracted from skin tissue were readily ox idized and degraded by 0.01% sodium hypochlorite. In a model system, N aOCl oxidized L-DOPA to a quinone, which turned black-brown, and degra ded GHB and GDHB to unknown compounds. Darkening of washed mushrooms m ay be due to the reaction of a quinone derived from oxidation of L-DOP A or its derivatives by NaOCl.