Koji box (kojibako)

A koji box (kojibako) is a dedicated box used in sake production when rice is fermented with koji mold (kojikin). It is used mainly in a technique called the hako-koji method (箱麹法, box koji method). The inside of a koji box is well ventilated and designed so that temperature and humidity can be properly controlled, providing an environment in which the koji mold can grow actively. Koji plays a very important role in sake brewing: it promotes saccharification and forms the basis of alcoholic fermentation. For this reason, the koji box can be regarded as one of the basic pieces of equipment in sake making.