Koji involves a fungal strain—usually Aspergillus oryzae—which is cultivated on steamed grains like rice to produce enzymes that break down starches and proteins. This process is essential in making traditional fermented foods like miso, soy sauce, and sake. This transformation gives koji rice a naturally sweet, umami-rich flavor with a subtle, nutty aroma. It’s a foundational ingredient in Japanese fermentation, used to make sake, miso, soy sauce, and amazake, where it enhances depth, complexity, and savory-sweet taste. Mix with water and salt to create the all-purpose seasoning, shio koji used to marinate meat or fish or as a final seasoning.