What traditional method is often used to make Koji?

The traditional method used to make Koji involves spreading steamed rice with koji-kin and allowing it to ferment. This process is crucial because the koji mold (Aspergillus oryzae) is introduced to the cooked rice, where it begins to convert the starches in the rice into sugars. This sugar is essential for the fermentation process, as it serves as the food source for yeast during sake production.

Steaming the rice ensures that it is cooked properly to support the growth of the mold. Once the koji-kin is sprinkled over it, the rice is typically kept in a warm environment to facilitate fermentation. This method is integral to sake production and highlights the importance of koji in converting starches to sugars, setting the foundation for successful fermentation and the development of flavor in sake.

Other options, while related to rice preparation in some capacity, do not capture the traditional method specifically for producing Koji. Grinding rice into powder does not create the textured form of rice needed for koji. Soaking rice in water is primarily a pre-cooking step and does not involve the fermentation process. Fermenting rice with yeast in barrels occurs later in the sake-making process and does not pertain to the generation of koji.