- “Bed” kōji method
A system of making koji using neither trays nor boxes. The whole process is carried out on large tables or beds (toko). Of all the systems of sei-kiku, this is thought to be the oldest, but the process is even simpler than for “box” method koji. In the later stages, temperature and humidity tend to rise at the bottom of the layer of koji and where it comes into contact with the wood of the bed, making control difficult.
There are two variants, one where the entire process is carried out on the same single table until the koji is taken outside at the final de-koji stage, and a second where the batch is transferred to a separate bed shin-doko (新床, “new toko”）, after the mori stage. In this latter case, it is necessary to remove dividers to make the new bed, in which case an area of 4-4.5m2 is necessary for every 100kg of white rice to be handled. The new toko is made by removing the insulating material from the original table, and making spaces between the boards to allow for the flow of air. In other cases, a wooden or bamboo lattice may be built about 5-10cm from the surface of the table.