The general procedure for making koji :

-Steamed rice, cooled to about 35–40°C, is transferred into the incubation device or room where the temperature and humidity are controlled at a level suitable for growth of the molds.

-After inoculation with seed molds, the mixture is incubated for about 40–48 h, with occasional mixing, during a controlled temperature rise to prevent it from rising too much.

-Finally, the temperature of the molded rice rises to 40–42°C, and white mycelia develop to cover and penetrate into the grains. Koji mold grows on the surface of rice at 20 h, and the mold is spread over the surface of rice at 44h after starting koji making.

-The resultant molded rice grains, koji, contain sufficient enzymes and various nutritive substances (e.g., vitamins and lipids) for mashing and yeast growth and fermentation.