Koji basics
How to Make Shoyu Koji (Room Temperature / Yogurt Maker)
Shoyu koji (soy sauce koji) is rice koji fermented in soy sauce. It is milder than soy sauce, with the added umami and sweetness of koji. Spoon it over rice, eggs or tofu, or use it in marinades and stir-fries. About 1–2 weeks at room temperature, or about 8 hours in a yogurt maker at 60°C.
- Serves
- Makes about 400 g
- Time
- 5 minutes to prepare (1–2 weeks at room temperature, or 8 hours in a yogurt maker)
Ingredients
- Rice koji (fresh or dried)200 g
- Soy sauce200–250 ml
Method
- If the koji is in clumps, break it up with your hands.
- Put the koji in a clean jar, pour in enough soy sauce to just cover it, and mix well.
At room temperature
- Rest the lid on loosely (do not seal it) and keep the jar at room temperature out of direct sunlight. Stir from the bottom once a day with a clean spoon. If the koji soaks up the soy sauce and shows above the surface, add a little more soy sauce.
- It is ready in about a week in summer, or about two weeks in winter — when the grains are soft, the texture is thick and it smells sweet.
In a yogurt maker
- Put everything in the container, close the lid and set it to 60°C for 8 hours. Stir once halfway.
When it is ready (both methods)
- Close the lid and keep it in the fridge.
Tips
- Rice koji is steamed rice grown with koji mould. Look for it, fresh or dried, at Japanese grocery stores or online. Ready-made shoyu koji is also sold at some Japanese grocery stores.
- Use it in place of soy sauce, in about the same amount. It is milder than soy sauce, with more sweetness and depth.
- Spoon it straight onto rice with a raw egg, chilled tofu, natto or grilled vegetables. It also makes a good marinade for meat and fish.
- It burns easily, so add it at the end when stir-frying.
- Keeps for about 3 months in the fridge.
Shoyu koji is simply soy sauce and koji. It takes about 5 minutes to prepare — then you just stir and wait. We use it in &LAB TOKYO recipes such as Sea Bream Chazuke. For shio koji, see How to Make Shio Koji.
In UMAMI & KOJI LAB in Tokyo, you learn how koji works and make koji seasonings like this by hand to take home.
