Sake is made from four ingredients: rice, water, koji, and yeast. Distilled spirit can be added as a fifth ingredient, which is made from rice, more and more to make the product 100% rice.
As we discuss in our in-depth sections on Growing Rice and as we describe our breweries, there are different quality grades of rice, standard rice, and sake rice, “shuzou koteki mai.” Within shuzou koteki mai, there are five quality grades. There are also more than 150 varietals of rice being used to make sake.
Water is the next ingredient. Japan has soft water relative to the rest of the world, but there are variations by area and source. Almost all craft breweries were built where they are because of the source of water. Most breweries have their own wells with water coming from nearby mountains. In many remote towns, the water is so good that brewers can use tap water.
Koji, or aspergillus oryzae, is a mold that comes in powder form that sake makers sprinkle on steamed rice to convert starch into simple sugar. Koji is used to make soy sauce, miso, and shochu, as well.
Yeast is the next ingredient, about which much could be said. There are standard yeasts that brewers can buy from the Central Brewers Association, yeasts created by local research institutes, and in-house yeasts that brewers maintain themselves.
Distilled spirit, used in honjozo, is made by distillers, not the brewers, and is often made from rice. It is clear and neutral in taste and color.
Lactic acid is also added to the yeast starter, or “shubo,” in the sokujo method, but this is not considered an ingredient.