Along with Shio Koji, Shoyu koji has now become widely known as a fermented seasoning using Koji. It is a versatile seasoning that can be used for various dishes or as it is, besides Shoyu koji is not too difficult to make. In this article, Kawashimaya arranged all you need to know about Shoyu koji, step-by-step guide to making it and recipes you can try at the comfort of your abode!

How to make Shoyu koji



Rice Koji 150g
Shoyu 150cc
・ Jar or Container
・ Shoyu to be added later Appropriate amount




Put the rice koji in a clean storage jar.


Pour the Shoyu into the container.


Mix well, cover and leave at room temperature for about a week.
On the following day, stir the mixture once a day with a clean spoon.


After some time, the koji may absorb the Shoyu content so please add appropriate amount of Shoyu until it covers the surface of the koji completely.
The amount of Shoyu absorbed depends on how dry the koji is, so observe the condition of the ingredients and replenish Shoyu where necessary.


After about a week, the solution becomes thick. This signals that Shoyu Koji is ready for use. In the colder months, this process may take 10 days to a week.


Please store Shoyu koji in the refrigerator when completed.
The standard storage period is about 3 months.

Charms of Shoyu koji


Benefits from Koji contents:
・ Adjusts the intestinal environment with the power of enzymes.
・ Kojic acid contained in koji suppresses the production of melanin to prevent spots and freckles.
・ B vitamins are known to be effective in relieving fatigue and preventing anemia.

10 times more delicious!

A few years ago, Shio Koji became a hot topic, and then came the rise in popularity of amazake, all suggesting the indispensable existence of Koji. In the same way koji is used as a fermenting agent, Shoyu Koji is introduced.

Shio Koji, which is made only with koji, salt and water, has a simple yet deep taste of koji. However, Shoyu koji adds the "umami" flavour profile that is unique and unlike any other. Shoyu deriving from soybeans contains a large amount of protein, and the enzyme in the koji decomposes the protein to produce a large amount of "glutamic acid". The amount of "glutamic acid" is said to be 10 times that of Shio koji.

For more information on Koji, please refer to the following columns!

What is koji article

What is Koji? Introducing the Kinds of Koji and How to Use It
Koji is an indispensable word when talking about Japanese fermented food. You can't finish making Japanese fermented food, such as miso, shoyu, mirin, sake, etc., without creating the koji as its first step. This article is about the complete guide about koji and everything you need to learn about it. Let's dive further into the Japanese fermentation food culture!
Read More

What is koji Rice

What is Koji Rice? What is It Used For? ~ Koji Rice, The Amazing Japanese Fermented Food ~
Koji rice is steamed rice that has been propagated and fermented with koji starter. You can use koji rice into various foods!
Read More

Shio koji article

What is Shio Koji and How to Make Shio Koji?
Shio Koji is not uncommon in Japanese cooking. In fact, its rustic nature goes beyond oriental cooking and successfully made its way into western cooking. Learn how to include this special ingredient into your everyday meal, explore what constitutes shio koji, its versatile uses and for those who’d like to try it hands-on, shio koji making at home!
Read More

Salt Reduction Effect

A small amount of Shoyu Koji is enough to develop the burst of umami. Therefore, the amount of salt used in a dish can be reduced as a result. This salt reduction quality also makes it a best friend in the kitchen for multiple uses. Below are our recommendations on how to use Shoyu Koji.

Seasoning or Topping

Shoyu Koji is great not only as a seasoning in cooking, but also can a finishing touch to chilled tofu or when served with rice.

shoyukoji for seasoning or topping


Mix with Natto

Shoyu Koji is enjoyable when mix with natto.
The flavour profile is so unique and delicious that some consider Shoyu Koji incomparable to regular Shoyu.


shoyukoji mix with natto



Marinating for fried food

A little goes a long way. Shoyu Koji can be used as a marinating ingredient for fried food such as Japanese fried chicken, karaage. The koji content helps to soften the meat and in turn, create a wonderful burst of umami!


shoyukoji for marinating

Recipes using Shoyu koji


If you replace the regular Shoyu with Shoyu koji, you won't find it difficult to incorporate into your everyday cooking. You can use it for meat, fish, vegetables, and more. The unique taste of Shoyu Koji is sure to give the dishes a slightly different finish, and a little bit of surprise.

  • Grilled pork with Shoyu and ginger

    Grilled pork with Shoyu and ginger

    The power of koji softens the meat and increases its sweetness.

  • Boiled mackerel

    Boiled mackerel

    It's a different kind of dish with simmered fish, which resembles miso-simmered fish.

  • Mayonnaise Shoyu

    Mayonnaise Shoyu

    An easy dressing by mixing mayonnaise.

  • Stir-fried sweet and spicy peppers

    Stir-fried sweet and spicy peppers

    It can also be exchanged for burdock and lotus root.

Feel free to use the following recipes as a guide or inspiration for your next cooking.

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%% recipeID=recipe-8krfx2dqz, title=Boiled mackerel $$

%% recipeID=recipe-8krfx9rg3, title=Mayonnaise Shoyu$$

%% recipeID=recipe-8krfxj980, title=Stir-fried sweet and spicy peppers $$

Shoyu koji FAQ

I observed that the Koji residue remains, what is going on?
This may suggests that the Shoyu content is insufficient. Please add Shoyu until the koji is soaked entirely.
What is the white mold grown on the surface of the mixture?
The white mold is actually a type of yeast called "membrane yeast". It is not harmful to the body, therefore please continue stirring the mixture with a clean spoon.
Red and green molds have grown in the container. What should I do?
When molds have formed, please discard it. To prevent mold from growing, add Shoyu so that the koji is entirely soaked. When stirring the mixture, use a clean spoon to prevent germs from entering.

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