the main enzyme in the reaction of browning of mushrooms is tyrosinase which belongs to the polyphenol oxidase family. Tyrosinase is a copper containing protein. The two copper atoms within the active site of enzyme interact with oxygen to form a highly reactive chemical intermediate that oxidizes the substrate The enzymatic browning takes place in two steps: the hydroxylation of monophenols to o-diphenols and the oxidation of o-diphenols to o-quinones. The former is reversible, but the latter is irreversible, causing permanent change of mushrooms colour from white to brown