Abstract
The frozen shiitake mushroom (Lentinus edodes) darkens remarkably at defrosting and this browning is considered to derive from phenolase. In order to prevent this discoloration effectively, the properties of phenolase in shiitake mushroom should be clarified. As no detail information on shiitake has been obtained so far, the present paper deals with the several properties of this enzyme.
Phenolase was prepared as shown in Fig. 1, and the enzyme activity was measured colorimetrically.
The optimum pH of phenolase was about 4, 8 (Fig. 2), and optimum temperature was 50°C (reaction time 8 min., Fig. 4). As to the substrate specificity, all tested o-diphenols were oxidized and of all, the highest activity was noticed by catechol. It was inactive for p-cresol and hydroquinone (Fig. 3).
Phenolase lost the activity by the following treatments; blanching at 80°C, 1min. or 90°C, 30 sec. (Fig. 7, 8), CO airation (Fig. 10) and addition of sodium bisulfite (Fig. 9).
