Sanpai (bacterial spoilage of sake)

Sanpai (酸敗) refers to a phenomenon in sake production in which lactic acid bacteria multiply excessively, particularly in the moromi (fermentation mash), causing fermentation to go awry. As a result, acidity becomes higher than normal and the flavor and aroma may be spoiled. When sanpai occurs, the sake often tastes strongly sour and carries unpleasant aromas, and its quality declines significantly. It occurs most readily when hygiene control is inadequate or temperature control is not appropriate, so care is needed throughout the production process. To prevent sanpai, proper cleaning and sterilization, and fermentation management at appropriate temperatures, are important.