Shubo no karashi (resting of the yeast starter)

Shubo no karashi (resting of the yeast starter) refers to the state in which the shubo (yeast starter) is left for a certain period in sake production, between the time it is divided out (motowake, also called maru-cooling, 丸冷まし) and the time it is used. The purpose of this resting period is to stabilize the quality of the shubo. For sokujo shubo (quick-method yeast starter), about 5 to 7 days is generally considered appropriate. During this period, the shubo is carefully temperature-controlled to bring it to its best condition, and as microbial activity settles, it becomes ready for the next stage, the main mash preparation. In sake brewing, there are also related steps such as the "resting of polished rice" (白米の枯らし) when using polished white rice, and "dekarashi" (出枯らし), the resting after the koji is taken out (出麹). Each of these helps even out the distribution of moisture in the rice and bring it to a condition suited to brewing. In this way, the resting step is an important stage that bears directly on the flavor and quality of sake, and it must be carried out with care.