Irawaki (rapid fermentation surge in the moromi)

Irawaki refers to a phenomenon in sake moromi (fermentation mash) in which fermentation proceeds rapidly. In particular, fermentation gets ahead of saccharification, causing the fermentation temperature to rise sharply and producing a front-loaded (zenkyu-type) fermentation course that differs from the normal one. This state is a sign that the yeast is working vigorously, but if it goes too far it can harm the flavor and aroma, so brewers must be careful. Irawaki is one of the important elements of fermentation management, and it requires constantly observing the condition of the moromi and keeping it in balance.