Multiple parallel fermentation (Heiko Fukuhakko)

Multiple parallel fermentation (heiko fukuhakko) is the fermentation process unique to sake, in which koji mold (koji) saccharifies starch while yeast simultaneously carries out alcoholic fermentation. Because alcohol is produced at the same time as sugar is formed, sugar does not accumulate in the moromi (fermentation mash), making it possible to reach a high alcohol concentration. As a result, by the time the moromi finishes fermenting, its alcohol content often reaches around 19 percent. Multiple parallel fermentation is a very important method in sake brewing, and this characteristic gives sake its distinctive depth of flavor and aroma.