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What’s Koji Miso

Koji miso, miso paste, Japanese food Food & Recipes
Food & Recipes

“Koji miso” that you can see some products on markets recently.

Aren’t you curious; Is this koji miso different from ordinary miso?

What is it taste like?

Honestly, I have never heard “Koji miso” until I posted about Miso paste here.

What’s Exactly Koji Miso

The term, Koji in koji miso comes from Koji, which is originally one of the essential ingredients for making miso.

In other words, all types of miso paste contain Koji, you can’t make miso paste without it.

Japanese miso paste has roughly been divided into three types depending on raw materials,

JapaneseMain Raw Materials
Rice MisoKome misoSoybean, Rice koji, salt
Barley misoMugi misoSoybean, Barley koji, salt
Soybean misoMame miso Soybean, koji, salt

Actually, Koji miso is not officially categorized into the basic Japanese miso.

Now, what exactly Koji miso is?

It seems like a commercial name to allow miso-paste manufacturers to show their effort and their special products.

Even if their product is categorized in a type of rice, barley, or mame, they want to call their special miso paste koji miso when it is made of carefully selected Koji, or a high amount of Koji.

Also, some Koji miso has a unique grainy texture from Koji, so you can enjoy miso paste more.

Koji has been rooted in the Japanese lifestyle for Japanese long history and has been contributing tremendous health benefits.

Miso is one of the representative creations of Koji, and it’s enough reason to emphasize koji as ingredients in their products.

So, koji miso is not referred to as the type of miso paste, it’s more a commercial name to appeal to their products.

Is Koji The Same As miso?

Koji is the mold called Aspergillus oryzae which is grown on steamed rice, barley, soybeans, etc.

As you know, miso paste is a fermented food made from fermented soybeans and Koji.

Koji, which is used not only for making miso but also for making soy sauce and Japanese sake, is certified as a national bacterium in Japan.

So, technically, Koji is not miso, but it’s the essential ingredient for making miso paste.

There are different types of koji depending on the material used, which are mainly rice, soybean, and barley.

Rice koji can be most popular to you, and here is the guide about rice koji but Shio-koji.

Koji produces many enzymes, including proteolytic enzymes (proteases) and starch-degrading enzymes (amylase), which decompose protein into amino acids and produces Umami flavor.

One of the traditional Japanese food preservation methods is marinating ingredients with miso. The degrading enzyme (protease) in miso 󠄀breaks the protein.

Shio koji, which I talk about in this post as a traditional meat tenderizer, uses this benefit.

How To Make Koji Miso

Miso is made by mixing cooked soybeans with koji, salt, and water, and then, will be fermented for months.

The types of Miso differ depending on koji as I mentioned former section.

You can make homemade miso easily while using rice koji.

Plan for the time to ferment soybeans.

Commonly, making homemade miso is preferred to start during the wintertime.

Cook the soybeans, mash them, and mix with rice koji and salt.

Transfer the paste to a container to ferment.

how to make Japanese miso paste at home, recipe, fermented food,


Rico McConnellRico McConnell
Traditional Japanese miso paste with simple 4 ingredients, a simple process. This miso paste recipe makes for a great mild yellow miso using koji rice.
Course Condiments
Cuisine Japanese


  • 1 instant pot
  • heavyweight *use salt/ beans in a ziplock bag


  • 0.44 lb Soybeans
  • 1 package *Iseya Rice Koji *200 g, 0.44 lb
  • 10-12% sea salt
  • The cooking water after the beans cooked.


  • Combine the rice koji and salt using a food processor. Or use your hands.
  • Rinse the soybeans thoroughly several times under running water. Soak the soybeans for 18 hours.
    *Hydrate the beans even when using an instant pot since they should be cooked really soft.
  • Drain the beans. Add the soybeans to the inner pot, and fill the pot with water to about 3 inches above the beans.
  • "Bean" mode, 45 minutes.
    *Cook the beans longer for easy-mashing.
  • You can cook the beans on the stovetop. Bring the beans and water to a boil over high heat, and skim off the scum continuously. Simmer the beans for about 3-4 hours, uncovered, until the beans are really soft.
  • Drain the water, but, KEEP THE COOKING WATER.
  • Make the cooked beans paste with the food processor while they are still hot. Or, mash the cooked beans thoughtfully.
  • Add the cooking water a little if the beans are not enough to mash.
    *In this recipe, it's not gonna make "a miso ball". Make the bean paste softer than you think.
  • Add the koji and salt mixture while the bean paste is still warm, combine well.
  • Sanitize the container with high ABV alcohol such as vodka.
  • Scoop the handful of the bean paste with your fingers, and slam (literally slam) it into the container.
    *To get the air pockets out.
  • Press the paste to the bottom or walls thoughtfully to get the rest of the air pockets out.
    *The air pocket will cause growing mold.
  • Repeat this process.
  • Pat down the surface with your palm or spatula to smooth out.
  • Place a plastic wrap on top of the paste while being sure to cover fully without any air pockets.
  • Place the heavyweight on the top and lid it on. Label the date on the lid. 
  • Store the container in a dark and cool place for 3-8 months.


*Iseya Rice Koji
©Japanmcconnell/Rico McConnell- Content and photographs are copyright protected. Sharing this recipe is both encouraged and appreciated. Copying and/or pasting full recipes to any social media is strictly prohibited.
Keyword Beans, condiment, Easy, Fermented food, Instantpot, Koji, Miso, Traditional, Vegan, Vegetarian

Shopping List

The Hikari Miso additive-free

Miso is made of organic agriculture-grown soybeans and rice and sun-dried salt.
Additive-free. The product concept is based on safety and natural taste. You can enjoy mild natural red miso with plenty of umami produced by Koji. You can enjoy crushed soybeans in miso paste to add a unique texture.

Miso Paste Malted rice, Handmade in Kyoto Japan 300g(10.58OZ)

Yamasan is a company in Kyoto that handles green tea, miso, and soy sauce in Uji, Kyoto, Japan. The product concept is “food safety” particularly regarding raw materials such as domestic, additive-free, and organically grown. With traditional manufacturing methods and handmade products, enjoy delicious koji miso paste.

Contents: 300g (10.58OZ)-you can enjoy 20 bowls of miso soup when 15g miso per bowl. Additive-free, Gluten-free, No GMO/MSG.
Tubed paste type, easy to use and storage.

The Bottom Line

Koji miso is another commercial name for products especially using more Koji amounts or using special Koji.

Now, do you like to try this Japanese traditional condiment? Miso soup is the best way to know the taste of miso. Today, many types of miso are easily available online, try those and find your favorite miso.

Miso has many health benefits with high-quality protein as well as abundant nutritional components such as carbohydrates, fats, vitamins, minerals, and dietary fiber. Moreover, soy protein is difficult to digest and absorb as it is, but, miso paste can help to digest and absorb easier due to the power of enzymes, and efficient absorption can be expected.

When you go to Japan, visit a miso specialty store or a miso brewery and try the miso while listening to the expert’s commentary.

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