Moromi (fermentation mash)

Moromi (醪) is the term for the main fermentation stage in sake brewing. It is the mash made by combining shubo (yeast starter), koji, steamed rice, and brewing water in a tank and letting it ferment, and it forms the central step of sake making. Specifically, water, koji, and steamed rice are added to the shubo in several stages, and saccharification and fermentation proceed together, building the foundation of the sake. As the moromi ferments, alcohol and carbon dioxide are produced. The liquid portion becomes the sake (genshu, or undiluted sake), while the solids are separated as sake lees (sakekasu). Moromi is generally the stage before the product becomes sake, and under Japan's Liquor Tax Act the term refers to the state of the fermented raw materials. Because sake is completed through this fermentation process, moromi plays a very important role in sake brewing.