Sake is a fermented alcoholic beverage made from rice. Sake is a fermented food product like soy sauce, miso, and katsuobushi (dried bonito), which are standard seasoning for Japanese foods. Premium sake uses special rice called sake rice, which is suited for brewing premium sake. The grains of this rice, shuzo kotekimai, are a bit larger than table rice and processing rice. Sake rice is also called sakamai.
Sake rice is rice that is especially suitable for making sake. Each grain has a milky white shimpaku in its core. The degree of how much the surface of the rice is polished away has an important effect on the character of the sake.
Sake consists of 80% water. The mineral content of the water influences the growth of the koji mold and yeast, so the flavor of the sake will change depending on the water used. Since water quality also affects the feeling in the mouth, good water is essential.
The koji mold, which is the basis for the koji, converts the rice's starches into sugar (glucose), The yeast, which ferments the glucose into alcohol and carbon dioxide. Both are cornerstones of sake that influence the flavor and aroma of the final product.
Moromi is the fermenting mash that becomes the undiluted sake and determines the character of the sake. Brewing alcohol is sometimes added to this moromi. It brings out aromas in the sake and sharpens the flavor.