BIOCHEMICAL-CHANGES ASSOCIATED WITH MUSHROOM QUALITY IN AGARICUS SPP

Activities of tyrosinase (polyphenol oxidase) and protease, together w ith levels of phenol and protein, were determined in tissues taken fro m mushroom sporophores to identify quality differences in three strain s of Agaricus (Agaricus bisporus, strain U3, and A. bitorquis, strains AGC W20 and ATCC 32675). In all strains the skin tissue had greater t yrosinase activity, protein levels, and phenol levels than the flesh t issue. Strain U3 exhibited the highest native tyrosinase activity, whi le AGC W20 had the lowest. Tyrosinase in tissue extracts of all three strains was shown to be activated in vitro by sodium dodecyl sulfate a nd trypsin. The activation of tyrosinase in U3, particularly by trypsi n, was greater than in either A. bitorquis strain. A convergence of ac tivated and native tyrosinase activities occurred during storage, indi cating a possible in vivo action. Protease activity in skin and flesh tissues of the sporophore increased during storage, while protein leve ls fell. Inhibitor studies of the protease activities from senescent s porophores indicated that the major components were metallo- and serin e-proteases. Phenol levels from the skin of AGC W20 were found to be c onsistently lower than those of U3 and A TCC 32675. The implications o f these results in relation to mushroom quality at the time of harvest and during storage are discussed.