Tane-koji(seed koji) is produced by culturing koji mold on rice until the spores become sufficiently epiphytic. In order to do so, the rice must be processed so that the koji mold can grow easily and for a long time. This processing step is called the raw material processing stage. The raw material processing stage onsists of six operations.
850 kg of rice are soaked in two tanks.
The rice is then drained, steamed, cooled, inoculated with koji mold and initially cultured in this steaming vat.
1. Rice polishing
Brown rice is polished to roughen the outer surface of the rice. (rice-polishing ratio is 97-98%) Most of the surface of the brown rice is left on since it contains many nutrients that help the koji mold grow.
The rice is thoroughly washed to remove any chaff or dust. If any chaff remains, it may cause bacterial contamination.
For good growth of koji mold, the rice must absorb a sufficient amount of water. Characteristics of each lot of supplied rice slightly vary, even for the same variety from the same production area. Consequently, soaking time is determined by thoroughly testing the characteristics of the supplied rice.
After the rice has absorbed a sufficient amount of water, it is removed from the water for a while so the moisture between rice grains can evaporate. If water remains in between the grains, this will cause the rice to stick together when steamed.
After the rice is soaked and drained, it is steamed to convert the starch and the protein into a form that the koji mold can easily digest. In order to always obtain the same, uniform results, fine adjustments such as adjusting the steaming time depending on each lot of rice are required. Most microorganisms die during the steaming process, but in Bio’c, high pressure is applied at the end of the steaming process to sterilize any remaining bacteria.
The steamed rice is then cooled to the right temperature for koji mold to grow, in aseptic air which has been passed through a HEPA filter.
Koji mold is then cultured on the steamed rice in conditions which promote koji mold growth, until the spores become sufficiently epiphytic. There are many types of koji mold which vary in application and individual characteristics. Consequently, the proper temperature for koji cultivation will depend on the type of koji mold. If the conditions are not properly controlled according to the type of koji mold, the amount of spores produced will decline. Tane-koji(seed koji) must contain large amounts of healthy spores. Although there are only two operations, supervision during culturing can be said to be the most important step in Tane-koji(seed koji) production.
The computer room to maintain a clean culture room.
Inside the clean room factory
Inside the factory as seen from the clean room exit side. Normally not seen.
Our company is the only Tane-koji(seed koji) manufacturer which has achieved accurate temperature control by complete computer controlled automation. This computer management system was independently developed by our company. Until then, the person in charge had to check conditions every hour or two and adjust the temperature and humidity based on intuition and experience, in order to monitor conditions in the culture room for one week during Tane-koji(seed koji) culturing. Computer control has greatly contributed to a reduction in labor as well as improvement in the quality of Tane-koji(seed koji).
Working scene in the temperature controlled clean room
All work in the clean room is performed while wearing sterile clothes.
1. Koji mold inoculation
Tane-koji(seed koji) seed with "Genkin" (original source mold) produced by a sterile method in the laboratory is sprayed on steamed rice and thoroughly mixed until it is uniform.
The steamed rice which has been inoculated with the fungus is placed on stainless steel trays in the temperature controlled room, and then moved to the clean culture room and cultured for about one week. The temperature of koji and humidity in the culture room are strictly controlled by the computer.
Koji mold is cultured for a week and then transferred to the process line for drying in order to improve preservation, spore collection, and packing. Since moisture content after one week of culturing is high at approx. 25%, if it is stored as is, the koji mold spores may die or be contaminated by saprophytic bacteria. Consequently, it is dried to reduce moisture content so long-term preservation is possible. The well dried spores can be stored for six months or more in cool, dark place.
”Onkochishin” (seeking to discover something new by studying the past)
A culture room from the past has been reproduced. Everything is made from cedar boards.
Dehumidified air at a low temperature around 30-35°C is used to reduce moisture content while maintaining bacterial activity.
Only koji mold spores are collected using a sieve. In some types of Tane-koji(seed koji), the spores and rice are not separated, and shipped dried.
Collected spores are tested. Strict checking is required so the Tane-koji(seed koji) can be used as “moto (source)” to produce koji used for sake, miso, and soy sauce.
Mixing and Packing
Spores are mixed with pregelatinized starch as specified according to the purpose of the Tane-koji(seed koji) and requests by the manufacturer who will use them.
The packaged Tane-koji(seed koji) is sampled and checked.
When stored in a cool and dark place, the product can be used for up to 6 months.