Japanese sake is an alcoholic beverage brewed from rice. The brewing process for sake is unusual in that it makes use of heiko fukuhakko ("multiple parallel fermentation"), in which saccharification, or the conversion of starches into sugars, takes place simultaneously with fermentation in a single tank.
The multiple parallel fermentation process involves many complicated steps. First the rice is polished, leaving behind starch which will be converted into the sugar necessary for fermentation, and a yeast starter is created. Koji (rice cultivated with koji mold), steamed rice and water are added to the yeast starter in three stages, ensuring that the saccharification and fermentation proceeds in a smooth and balanced manner. Brewing rice into sake is a complex and painstaking process, requiring both sophisticated brewing technologies and artisanal craftsmanship, and it is this which results in the depth of flavor and character that is unique to sake alone.
Rice suitable for sake brewing is referred to as shuzo-kotekimai. This type of rice has large grains, a large shinpaku, which refers to the starchy center core of the rice grain, and less protein than is found in ordinary rice. Yamada Nishiki is one of the best-known brands of shuzo-kotekimai, but at Otokoyama Honten we primarily use the local Miyagi brand Kura no Hana.
Kura no Hana is a sake rice with hard grains resistant to cracking during the milling and polishing process, but it is at the same time very suitable for koji making and absorbs liquid evenly. With its low protein content, it produces a sake low in amino acids with a fresh, light character.
Yeast converts the sugars produced by koji into ethanol and carbon dioxide, and contributes to the flavor and aroma characteristics of sake.
The water used in the yeast starter, moromi fermenting mash, and other steps of the sake brewing process is called shikomimizu (brewing water), and the quality and character of this water is reflected in the final sake product. At Otokoyama Honten, we brew our sake using the soft spring water of our region, which results in sake with a soft, pleasant mouth-feel.