04 Yeast & Fermentation Starter
Yeast and Fermentation Starter
Top-grade yeast specifically intended for sake brewing is selected for the fermentation process.
Before the main fermentation, the brewer first prepares seed mash, called shubo or moto, by significantly increasing the amount of top-grade yeast. This is used as a starter for fermentation of the main mash. The word "shubo" means "mother of sake," while the word "moto" means "base" or "source."
It is important for shubo to be highly acidic in addition to contain top-grade yeast. Fermenting in acidic conditions suppresses the microbes that spoil sake, but unlike grapes, rice itself contains no acid. That is why strongly acidic shubo must be used. Methods of production highly acidic shubo include use of lactic acid bacilli and use of brewing-grade lactic acid.