Kōji is a traditional Japanese fermentation starter made from steamed rice, wheat, or soybeans that have been inoculated with specific molds, primarily Aspergillus oryzae. It is essential in the production of various Japanese foods, including sake, miso, and soy sauce. Kōji helps convert starches and sugars into alcohol and acids, enhancing flavors and preserving food. The process of making kōji involves spreading the inoculated grains in a warm, humid environment, allowing the mold to grow. This fermentation technique has been used for centuries in Japan and is crucial for creating umami-rich flavors in many dishes.