What fermentation process is unique to sake?

The double fermentation process is unique to sake, which is known as "multiple parallel fermentation." In this process, both starch conversion into sugar and sugar conversion into alcohol occur simultaneously. This is distinct from most other alcoholic beverages, where these processes happen sequentially.

In sake production, koji mold (Aspergillus oryzae) is used to convert the starches in steamed rice into sugars. During this time, yeast is also present, fermenting the sugars into alcohol. This simultaneous action is what distinguishes sake from beverages like beer and wine, where mashing and fermentation occur in separate stages.

Understanding this process is crucial for appreciating how sake is made and its unique flavor profile, which is heavily influenced by the dual fermentation happening at the same time.