Koji Chomiryo (Fermented Seasonings Made with Rice Koji)

Koji rice mold sounds unappetising but this traditional ingredient is the key to Japanese cuisine! Koji is a type of steamed rice inoculated with Aspergillus oryzae (a friendly mold) that produces various enzymes during its fermentation process which then work to create sweetness and umami. It’s used to make classic ingredients like soy sauce, miso, sake, and mirin, as well as amazake, different types of pickles, and the koji seasonings in this recipe!

What Are Koji Seasonings?

Koji seasonings are condiments and flavour bases made by fermenting ingredients with koji and salt. The fermentation of the koji mold produces enzymes which turn starch into glucose and break down proteins into amino acids like glutamates which creates the rich and layered umami flavour and sweetness. Koji is also full of vitamins and minerals and brings a variety of health benefits like boosting the immune system and good digestion. You can use koji to create different seasonings using such as onion, salt (shio), tomato, garlic, and soy sauce. Each brings a rounded and mellow taste making them an all-purpose seasoning for soup stocks, salad dressings, and marinades for beef, chicken, and other meats and seafoods.

Koji Seasonings Variations

Shio (salt) koji : made from rice koji and salt. It’s best to use shio koji for meat marinades because it makes the meat tender and adds a natural salty umami flavor. 

Shoyu koji : made from rice koji and soy sauce. You can use shoyu koji as a replacement for shoyu to add extra rich umami and depth when making things like stir fries and salad dressings.

Tamanegi (onion) koji : made from rice koji and onions. This one is best to use for salad dressings and as a replacement for bouillon/consomme and soup stocks to add a natural sweetness, umami, and flavor to soups and stews. I recently used this to make corn pottage and it was super delicious. 

Ninniku (garlic) koji : made from rice koji and garlic. This one is perfect for meat marinades and for making fried chicken like Japanese karaage. It adds a mellowed garlic flavor and delicious taste. 

Tomato koji : made from rice koji and tomatoes. This is great for use in soups, curries, and stews and salad dressings. It brings a natural sweetness and subtle tanginess to dishes. 

Amazake : amazake is slightly different from the others because it’s simply just rice koji. It is typically consumed on its own as a naturally sweet, fermented drink. But it can also be used in cooking just like the other koji seasonings to add subtle sweetness to a dish. I have a whole post dedicated to Amazake if you are interested in learning how to make your own amazake.

Traditional Japanese rice snack, frozen rice cake, and cooked rice for Asian cuisine.

Above are just a few, there are more that you can create such as shoyu and onion combined, or any other conbination and also you could use ginger, shiso leaves etc other ingredients. If you are interested in fermented food recipes, see my Japanese fermented recipe book.

How to Make Koji Seasonings

Making koji seasonings at home is simple and requires just two base ingredients: rice koji and salt. The basic process involves mixing the koji and salt with the chosen extra ingredient (onions, garlic, tomatoes, soy sauce) then letting it ferment at room temperature for about a week. Alternatively you can use a yoghurt maker, like I did, which is easier and quicker.

During the fermentation, the enzymes in the koji break down starches and proteins, creating the natural sweetness, umami, and depth of flavor. The mixture has to be stirred daily to encourage even fermentation, and once it reaches a balanced taste, it can be transferred to the refrigerator for storage.

How to Make Koji Seasonings in General

1. Prepare the ingredients – Place rice dry rice koji and salt into a clean sterilized glass jar. Break dry koji up if any clumps.
2. Mix with salt – Add the salt and stir well in order to coat the koji grains evenly with salt.
3. Add liquid or base – Pour in water, soy sauce, or the chosen vegetable puree and mix until fully combined.
4. Ferment at room temperature – Cover loosely and leave in room temperature(around 20–25°C / 68–77°F). Stir once a day to keep it active or set it in a yoghurt maker overnight.
5. Wait for flavor to develop – After about 5–7 days, taste the mixture. When it has a balanced salty-sweet umami flavor, it’s ready. It will be ready the next day if using a yoghurt maker.
6. Store in the refrigerator – Keep in an airtight container in the fridge. The flavor will deepen over time and can last for a few weeks refrigerated.

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