Yellow Koji Mold

Koji plays an important role in sake brewing such as saccharification of starch. The mold used for koji is a type of fungus found only in East Asia, it has long been an integral part of Japanese food culture including fermented foods and has been certified as Japan’s national mold in 2006.
The koji mold has some different types, including yellow koji mold, black koji mold and white koji mold, and they are used in different ways depending on the characteristics. Yellow koji mold is mainly used for sake, miso, soy sauce, mirin (sweet cooking sake) and vinegar. It has been used longer than the other koji molds and the name comes from the color of spores, which are yellow or light green. The scientific name is Aspergillus oryzae and oryzae means a rice plant. By the way, they say Japan is the only one that uses yellow koji mold to make alcoholic beverages.
The yellow koji mold is excellent in breaking down starch to produce sugars that are necessary for alcohol fermentation. The gorgeous aroma like fruity ginjo aroma is also one of the attractive features of yellow koji mold. In recent years, it has been used more and more in making shochu and well received for creating a rich and full-body taste just like sake. The weak point is that unlike other koji molds, yellow koji mold does not produce citric acid, which makes it easy for bacteria to grow. As sake brewing requires management at low temperature, the weakness of yellow koji mold is a major reason why sake brewing is done mostly in winter.