Toko koji ho (bed-based koji making method)

Toko koji ho (床麹法) is one of the methods used in sake brewing to make koji. In this method, no koji boxes are used; instead, all stages of koji making are carried out on a flat surface called a toko (bed). Specifically, steamed rice is spread out on the bed, and the rice is left to rest to promote fermentation, with its temperature adjusted during the process. Temperature is generally controlled by varying the thickness of the steamed rice and by using covering cloths, and the optimal fermentation environment is maintained by using a bed designed so that air can pass through its base. Because it allows koji to ferment evenly, this method is used as a traditional technique at many breweries.