Samashi (cooling the yeast starter)

Samashi (cooling) is a temperature-control technique used in sake brewing once the yeast in the shubo (yeast starter) has multiplied sufficiently. As the shubo ferments, its alcohol content reaches 8-10% and its acidity continues to rise. If it is kept at a high temperature in this state, the yeast may weaken or die. To prevent this, the fermenting shubo is divided among hangiri-oke (shallow wooden tubs) to lower its temperature, and this practice is called "samashi." In recent years, a method called "maruzamashi," in which the temperature is lowered with a cooling unit while the shubo remains in its tank, has become common. This method allows more even temperature control and is an important process in brewing high-quality sake.