Tsuwarika (off-aroma from abnormal fermentation)

Tsuwarika is a distinctive odor that arises when abnormal fermentation occurs in the moromi (fermentation mash) of sake. The aroma is caused by the proliferation of lactic acid bacteria and by the influence of bacteria known as hiochi, and it points to a problem in the production process. The main components of tsuwarika include diacetyl and acetic acid, which give it a smell similar to yogurt or butter. The appearance of this aroma indicates a deterioration in the quality of the sake, and it serves as a reminder of the importance of managing the moromi and the fermentation process.