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 polyphenol oxidase (PPO), and PPO isozymes during washing, as well as effects of sodium hypochlorite (NaOCl) on phenolic compounds in mushrooms were investigated. About 15% of the soluble phenols from the skin of mushrooms, mostly γ-L-glutaminyl-4-hydroxybenzene (GHB) and γ-L-glutaminyl-3,4-dihydroxybenzene (GDHB), were leached out during washing. Among four isozymes of partially purified PPO separated by native electrophoresis, the two faster migrating forms were leached out during washing. Phenolic compounds extracted from skin tissue were readily oxidized and degraded by 0.01% sodium hypochlorite