Rice or Barley Koji
Prep time: 
Fermentation time: 
Total time: 
Yield: 1 kg koji
  • Steaming baskets or trays
  • Cedar or unfinished wooden tray, or baking dish at least 13"x 9" with a 2 inch lip
  • two clean dish towels
  • tongs
  • 400g (about 1 lb.) dry white rice (a long grain variety like jasmine) or pearled barley
  • 5 grams koji starter (koji mixed with rice) OR 1 gram pure koji spores
  1. Place the grain in 3 times the volume of clean filtered water.
  2. Soak at least 6 hours, or overnight.
  3. If using rice, drain well, then rinse several times until the rinse water is clear.
Steam Grains
  1. Prepare your steamer. Add steamer baskets or tray to a large pot. Add enough water to the bottom so it is not touching the bottom of the steamer tray. Add dish towels to basket and cover with lid.
  2. Set pot on medium-high heat, and steam the towels for 20 minutes.
  3. With tongs, carefully remove one of the dish towels and set aside. Drape the other one inside the steamer basket.
  4. Add rinsed and drained grains to steamer. Spread evenly so steam can penetrate the entire mass of grain.
  5. Steam at least 45 minutes, or until the grains are al dente. You may need to add more water to ensure there's enough steam. Don't let it run dry!
  6. While grains are steaming, prepare tray. Drape the steamed, cooled dish towel in the tray. There should be enough extra towel so you can completely wrap the bed of grains on all sides.
  7. When it has been cooked, carefully pour grains into the tray and let cool down to 90°F/32°C.
Inoculate and Culture
  1. Once cooler, gently and evenly sprinkle ⅓ of the tane koji over the bed. Stir the grains well. Repeat with another ⅓, stirring well, and finally the remaining ⅓. Stir for a total of 3-4 minutes to thoroughly incorporate the koji spores.
  2. If you are using the pure spores, you can use a flour sifter to gently disperse the spores. They will seem lighter than air, so observe carefully as the spores fall onto the rice bed.
  3. Cover the grain bed with the towel. If you need to, you can also use the towel you used to steam them. Just ensure that you first wring the steaming towel out first to remove excess water.
  4. Add to your incubating chamber. Ideal temperature range during the first 24 hours is 86° to 91°F/30° to 33°C, with 75% humidity.
  5. After 24 hours, you should start to see signs of the mycelium forming all over the garins, and it should be fairly fragrant.
  6. Break up any clumps or mats, then create several lengthwise furrows in the bed to create more surface area for those oxygen-loving microbes.
  7. Check again at 36 hours, ensuring the temperature doesn't climb too high.
  8. Koji should be finished between 40 and 48 hours. If it begins to turn splotchy colors like dark olive, yellow, it has begun to sporulate (possibly because it was too warm). Make a decision as to whether enough mycelium has formed if this occurs.
  9. Remove tray from incubator, then allow to cool down. Break up any clumps to get to as close to individual grains as possible.
  10. Use koji immediately, or refrigerate in a tightly sealed container for up to 3 days in the refrigerator.
Recipe by Fermenters Club at https://fermentersclub.com/koji/