ACTIVITY OF ALPHA-GLUCOSIDASE IN SAKE KOJ I AND ITS ROLE DURING SAKE BREWING

Enzyme activities of koji samples from 12 sake breweries were determin ed, and the relationship between their production conditions was analy zed. alpha-Glucosidase activity showed a high correlation with glucoam ylase and alpha-amylase, and was especially in the case of the latter. Ginjo koji had higher relative activity of alpha-glucosidase to alpha -amylase, suggesting that alpha-glucosidase may play an important role in ginjo (high-quality) sake brewing. Addition of purified alpha-gluc osidase to koji enzyme solution increased the glucoamylase activity. G lucose was produced by the addition of both purified alpha-glucosidase and purified alpha-amylase to starch solution, but not by the additio n of only alpha-glucosidase. These results indicate that the conventio nal method for measuring glucoamylase activity measures not only gluco amylase but also alpha-glucosidase activity. The contribution rate of alpha-glucosidase to glucoamylase was estimated to be 10-20% of the gl ucoamylase enzyme activity of koji determined by the conventional meth od.