Sake is a naturally fermented alcoholic beverage brewed from rice, select water with a low mineral content, koji (molded rice made from Aspergillus oryzae) and yeast. The fermentation process for sake is unique in the fact that the conversions of starch into glucose and glucose into alcohol occur simultaneously. Due to this complexity, the key to making a good sake is to choose the appropriate ingredients and foster an environment in which the koji enzymes and yeast can effectively work together.

Sake making is an efficient process and yields a number of high value by-products. The rice bran (nuka) produced from milling the rice is most commonly used as in ingredient for both traditional and modern food products. From olden days, rice bran was said to be good for the skin and is now used in some cosmetics. The sake lees (sake kasu) produced from the pressing process is also used as a food ingredient and is used to make amazake, a lightly sweet non-alcoholic beverage.