Effect of Various Seasonings on Protease Activity in Raw Soy Sauce

Raw soy sauce, which is not sterilized, has a bright color and mild aroma, and possesses residual enzymatic activity to break down proteins and starch. Raw soy sauce is often used in combination with other seasonings. The enzymatic activity in raw soy sauce may be affected by the type of seasonings used in combination. In the present study, we examined the effect of cooking with other seasonings on the enzyme activity in raw soy sauce in a model experiment simulating actual cooking. In addition to raw soy sauce, we used white sugar, mirin (hon mirin, mirin-style seasoning, and boiled-down hon mirin), cooking sake, and grain vinegar as seasonings. Protease activity was measured under several heating conditions. When heated at 60°C, the degree of enzyme inactivation decreased as the ratio of the combination of white sugar, mirin-style seasoning, and boiled-down hon mirin increased. The results of the present study suggest that carbohydrate compounds commonly contained in each seasoning have a protective effect on the enzymes in raw soy sauce.