Simultaneous, Stepwise Fermentation

Chinese and Japanese brewing methods differ in important details, but they also share several important features. The starch-digesting molds and alcohol-producing yeasts are added to the cooked rice gruel together, and work simultaneously. Unlike the making of beer, where a liquid is extracted from the grain and only the liquid is fermented, the thick gruel of cooked rice is fermented whole. And the rice is introduced gradually into the fermentation, not all at once: new portions of cooked rice and water are added to the vat at intervals during the fermentation, which lasts from two weeks to several months. All of these practices apparently contribute to the yeasts’ ability to continue producing alcohol to high concentrations. When rice is added toward the end of fermentation, some sugar remains unmetabolized by the yeasts, and the resulting alcohol is sweet.