The Magic of Koji: Sake’s Secret Ingredient

One ingredient makes sake so unique that it simply couldn’t exist without it: koji mold.

Have you heard of it?

Koji is the unassuming but powerful mold (Aspergillus oryzae) that takes steamed rice and transforms it by breaking down its starches into fermentable sugars. This step is essential in sake brewing and creates a world of flavors that define sake’s signature profile.

Koji is sprinkled onto rice, where it grows and releases enzymes that do the hard work of breaking down starch. And though koji is also used in making miso, soy sauce, and other traditional Japanese foods, its role in sake is special, lending each brew a complex, almost alchemical quality. It’s thanks to koji that we get the delicate, balanced flavors in sake—whether floral, fruity, or earthy.

So next time you sip sake, raise a glass to koji, the little mold with a big impact.