Koji-jiru (koji juice)

Koji-jiru (麹汁, koji juice) refers to a liquid made by dissolving koji in water. Koji is produced using microorganisms of the genus Aspergillus and is used mainly in making fermented foods such as sake, shochu, miso, and soy sauce. In sake brewing, yellow koji mold (kikoji-kin) is used in particular; it produces saccharifying enzymes that convert the starch in rice into sugar. For shochu, black koji mold and white koji mold are used respectively, each bringing out different flavors and aromas. Koji-jiru plays an important role in the fermentation process and forms the foundation for creating sweetness, umami, and flavor.