Komaishu (aged-rice odor)

Komaishu (古米臭) is a characteristic odor derived from aged rice. In sake, it is regarded as a sign of declining quality. The odor is produced mainly from oxidized fatty acids and their breakdown products, and arises as the rice loses its freshness. In sake made with old rice, the aroma and flavor are impaired, which can make it unpleasant to drink. For this reason, it is important to use fresh rice in sake brewing.