Koji-buta (Koji tray)
Japanese: 麹蓋（こうじぶた）
A shallow wooden tray for making small batches of koji. Excellent temperature control and ventilation.
Koji-buta is a shallow wooden box made from cedar or cypress. Each tray cultivates about 1.5-2 kg of koji. The wood absorbs excess moisture and maintains proper ventilation, producing high-quality koji.
Used during portioning, trays are stacked on shelves in the koji room. The wood itself harbors microorganisms, contributing to each brewery's unique character. Even as automated systems spread, hand-crafted koji-buta making remains synonymous with premium quality. Portioning small amounts per tray allows fine temperature adjustment. Meticulous control impossible with large automated equipment is the greatest appeal.