Sake brewers typically buy rice from suppliers. When it is delivered to the brewery, the rice has not been steamed. It is hard and dusty. The brewers steam the rice to soften it so that it can break up in the water.
Typical bottle of sake will consist of 15-17% ABV, the rest is water. Water source is essential. With abundant rainfall in Japan and forests occupying 60% of the land, water is plentiful. Historically, sake makers established breweries in locations with access to good-quality water.
Koji is an essential ingredient in breaking down starches into sugars. Variety of koji is also used in the production of traditional Japanese seasonings, such as miso and soy sauce. Without this ingredient it is not possible to make the alcohol that is found in all sakes.
Top-grade yeast specifically intended for sake brewing is selected for the fermentation process. Yeast is used to convert sugar into alcohol during the fermentation process.The fragrance and aroma can e attributed to the yeast strain.