BIOCHEMICAL-CHANGES ASSOCIATED WITH MUSHROOM QUALITY IN AGARICUS SPP

Activities of tyrosinase (polyphenol oxidase) and protease, together with levels of phenol and protein, were determined in tissues taken from mushroom sporophores to identify quality differences in three strains of Agaricus (Agaricus bisporus, strain U3, and A. bitorquis, strains AGC W20 and ATCC 32675). In all strains the skin tissue had greater tyrosinase activity, protein levels, and phenol levels than the flesh tissue. Strain U3 exhibited the highest native tyrosinase activity, while AGC W20 had the lowest. Tyrosinase in tissue extracts of all three strains was shown to be activated in vitro by sodium dodecyl sulfate and trypsin. The activation of tyrosinase in U3, particularly by trypsin, was greater than in either A. bitorquis strain. A convergence of activated and native tyrosinase activities occurred during storage, indicating a possible in vivo action. Protease activity in skin and flesh tissues of the sporophore increased during storage, while protein levels fell. Inhibitor studies of the protease activities from senescent sporophores indicated that the major components were metallo- and serine-proteases. Phenol levels from the skin of AGC W20 were found to be consistently lower than those of U3 and A TCC 32675. The implications of these results in relation to mushroom quality at the time of harvest and during storage are discussed.