Sake Brewing and the Fushimi Springs
Sake cannot be made without a plentiful supply of water. In its finished form, sake is roughly 80 percent water, so the importance of the purity and quality of the water cannot be overemphasized. Unlike grapes, which are full of liquid, steamed rice is solid. For this reason, a lot of water must be added to create a suitable mash. The volume of water used in all the parts of the sake-brewing process—including washing, soaking, and steaming the rice—adds up to more than 30 times the weight of the rice itself.
Since time immemorial, Fushimi has been blessed with water that bubbles up through layers of granite and clay. As the water percolates upward, much of its iron content is filtered out—iron colors the sake and strongly degrades its taste and fragrance. Fushimi spring water does potassium, which supports yeast propagation and encourages the development of the kōji mold.
Because Fushimi breweries mostly make rounded, mellow sake from this soft water, Fushimi sake is known as onnazake, or “female sake.” Brewers in other parts of Japan, like Nada in Hyogo Prefecture, use harder spring water to make sake that is known as otokozake, or “male sake.”