Hako koji method (box koji-making)

The hako koji method (箱麹法) is a koji-making technique in which koji mold is cultivated in specially designed koji boxes (koji-bako) during the koji-making (seikiku) stage. Because the method allows the growing environment of the koji mold to be controlled closely, it is often used in the production of premium sake. In the hako koji method, boxes that are generally larger than the traditional koji lid (koji-buta, a small wooden tray) are used, and each box can hold 15 to 45 kg of koji. This approach makes it possible to produce a large quantity of koji efficiently at one time, but it requires a certain amount of care and attention to manage, so the knowledge and experience of skilled brewers are considered important. As a result, sake made with the hako koji method is valued as a high-quality sake with rich flavor and aroma.