Tsuyoi mizu (strong water)

Tsuyoi mizu (literally "strong water") refers to brewing water that is rich in components that support fermentation in the moromi (fermentation mash) of sake. Specifically, it contains abundant minerals such as potassium, magnesium, chloride, and phosphoric acid. These components stimulate the activity of the yeast, creating an environment in which fermentation proceeds vigorously. Because water has a significant influence on the quality and flavor of sake, the presence of strong water is very important in sake brewing.