Optimal pH
Japanese: 至適pH
The pH at which an enzyme shows maximum activity. Activity drops rapidly when pH deviates from the optimum.
Optimal pH is the pH value at which enzyme activity is maximized. An enzyme's protein structure changes with pH, and significant deviation causes structural collapse and inactivation.
Koji mold's proteases include acid protease (optimal pH 3-4), neutral protease (pH 6-7), and alkaline protease (pH 9-10). In miso's aging environment (around pH 5), acid protease primarily operates.
Amylase's optimal pH of 5-6 suits miso well, while lipase prefers neutral to mildly alkaline conditions. The fermentation environment's pH naturally selects which enzymes work and how much. Knowledge of optimal pH is the gateway to understanding fermentation mechanisms at the molecular level. Expert understanding becomes the key to expanding fermentation's possibilities.