- Kiri-kaeshi machine
In the early stages of koji production, some twelve to sixteen hours after toko-momi and tane-kiri, the koji -kin begins to grow on the heap of steamed rice , giving off heat. As a result, the temperature and humidity in the inside and outside parts of the heap become uneven. At the same time, the air between the rice grains is consumed, and carbon dioxide and heat build up. It is necessary to spread out the pile and break down the clumps, a task called kiri-kaeshi. This is extremely laborious work, and a machine to do it was long since developed. Koji-mai is put into the hopper on top of the kiri-kaeshi machine , and the clumps are broken down by rotating spikes in a mixer. The loosened koji then falls out at the bottom.
In the case of machine-made koji where there is only one toko bed, a mixer installed above the bed plays the part of the kiri-kaeshi-ki, and breaks down the mass directly. Where there are two beds, a mixer on the upper one does the work of the kiri-kaeshi-ki, breaking down the clumped mass and dropping the loosened koji onto the lower level.