Koji mold (Kojikin)

Koji mold (kojikin) is a type of filamentous fungus used mainly in the production of traditional Japanese fermented foods and alcoholic beverages. It belongs to the genus Aspergillus, known in Japanese as the koji mold genus. When koji mold is grown on steamed rice, it promotes fermentation and plays the key role of saccharifying (converting to sugar) the starch in the rice. This process is essential in brewing sake, miso, soy sauce, and mirin. The most commonly used koji mold is Aspergillus oryzae, which is widely used in making sake, miso, soy sauce, and mirin. The enzymes produced by koji mold break down the starch in rice into glucose, which supports the fermentation process and also contributes to the formation of aroma compounds characteristic of sake. As it grows, koji mold produces yellow-green spores, which is why it is also called "yellow koji mold" (ki koji kin). Because of these properties, koji mold plays a very important role in Japan's brewing industry and is indispensable to making sake with rich flavor and aroma.