STUDIES ON THE CONTROL OF SHOCHU FLAVOR . 3. SUPPRESSION OF YEAST GROWTH BY ACCUMULATED GLUCOSE, AND FORMATION OF GLYCEROL DURING ALL-KOJI SHOCHU FERMENTATION

The number of viable yeast cells (Saccharomyces cerevisiae) in the mas h using a 25-hour-cultivation rice-koji (25 h-koji) was higher than in a 43 h-koji mash, which is the conventional procedure. The lower viab le cell number in the 43 h-koji mash was estimated to be due to the hi gher concentration of glucose in the initial stage of the mash. The av erage concentration of glucose in the initial stage of the 43 h-koji m ash was about 10%, while that of the 25 h-koji mash was about 5-6%. Gr eater formation of glycerol was observed in the 43 h-koji mash than in the 25 h-koji mash. It is suggested that the higher concentration of glucose suppressed ethanol production and accelerated the formation of glycerol by the yeast in the 43 h-koji mash. The results of a model f ermentation with modified YEPD medium (glucose 5-15%, pH 3.5-5.5) show ed that the higher concentration of glucose significantly suppressed t he growth of yeast and production of ethanol at a lower pH, and that t he suppression by glucose at a lower pH in the all-koji mash, in which the pH was about 3.5, was considerable.