How to Rehydrate Dried Rice Koji

This tutorial is made by Kawashima The Japanstore using advices from the manufacturer of the dried koji themselves. Feel free to use this as a reference when you cook with dried koji in your kitchen.

What to Prepare to Rehydrate Dried Koji

What to Prepare to Rehydrate Dried Koji


  • ・Dried Koji (500g)
  • ・Big Bowl or Tray


To prevent the growth of unwanted microorganisms, thoroughly wash your hands and your equipments. We recommend you to disinfect your equipments by boiling them in hot water.



Process of Rehydrating Dried Koji

  1. Put dried koji into the bowl
  2. Add lukewarm water, then mix them together
  3. Let the mixture sit for a while
  4. Your koji is ready to use!


Step 1 Put dried koji into your bowl



Put dried koji into your bowl


Before putting the dried koji into the bowl, gently loosen the koji by pressing the bag with your fingers.



Gently loosen the koji by pressing the bag with your fingers


After that, put 500gr of dried koji into your bowl



Use your hands to separate the grains


Make sure the dried koji rice doesn't stick together. You can use your hands to separate the grains



Step 2 Add lukewarm water, then mix it



Add lukewarm water, then mix it


Add about 200cc of lukewarm water into your bowl. The ideal water temperature is about 50 to 60℃. With that warmth, the finished koji will look plump and nice.



Mix them well


Mix them well until all the dried koji is covered in water



Step 3 Let the mixture sit for a while



Let the mixture sit for a while


Cover the bowl with wrapping plastic and let it sit for about 1-2 hours. You should stir the mixture after 10 to 15 minutes, then let them rest again.



Step 4 Koji is ready to use



Koji is done


Dried koji has rehydrated



Koji is done


If you can crush the koji with your fingers, that means it is ready to use!



Important Points When Rehydrating Koji

  • ・Don't use boiling water
  • ・After you rehydrate the dried koji, please use them in the same day
  • ・After opening the package, use them as soon as possible
  • ・Do not use dried koji that has expired
  • ・Keep dried koji in a cool dark place. Do not put in direct sunlight

If you have dried koji, you can use them to make salt koji, homemade miso, and even amazake in your own kitchen.

Cook a delicious food with high quality dried koji that is made by long established shop.



How to use dried Koji

What is Dried Koji?

Dried koji is a type of koji that has been dehydrated. Koji can be divided into two types: regular koji (raw koji) and dried koji. Regular koji that is not dried is susceptible to various unwanted bacteria. It can also easily deteriorate in quality due to self-fermentation. Therefore, regular koji is harder to store. Because of that, dried koji was created.

Dried koji is very strong against various bacteria that have bad effects on the fermentation. It can also prevent self-fermentation. In addition to that, the taste of dried koji is pretty much the same as regular koji. With that kind of advantages, right now it is very understandable why most household would use dried koji. Lately, there are also a lot of restaurants that use dried koji so the demand for dried koji is getting higher.

How To Store Dried Koji

When storing dried koji, do not put it in places with high humidity

If you store koji in a very humid place, there might be possibilities that the koji taste and quality will change. Avoid putting it in direct sunlight and store them in cool dark places like refrigerator or freezer. If you follow this storing instruction, the taste and quality of dried koji will not change, and you can enjoy the dried koji in its best condition.

The Difference Between Dried Koji And Regular Koji

Regular Koji Dried Koji

Regular Koji

Dried Koji

25% Moisture Percentage Under 10%
2 Weeks (Refrigerated) Best Before 1 Year (Room Temperature)
Similar Enzyme Power Similar
Soft Physical Texture Hard




Regular Koji



Advantages Because the koji is fresh, it has the capability of turning starch into glucose. Other than that, it can be used to make high quality fermentation food that produce various enzymes and nutrients.

Disadvantages Due to high moisture, regular koji is prone to unwanted bacteria, so the quality can change because of self-fermentation. It is hard to store.



Dried Koji



Advantages Dried koji is not prone to unwanted bacteria. Because dried koji will not self-ferment, the storing is easier. It is also sold in many supermarket so it is easier to find.

Disadvantages If dried koji is added with hot water, the nutrients and enzymes that are kept in koji may be damaged. It needs the correct water temperature adjustment before use.



How much the nutrients and the enzymes damaged in dried koji may depend on what kind of rice and koji starter that is used. The environment where koji is made and stored may also affect them, so we can't conclude for sure. Nevertheless, the nutrients and enzymes in koji will remain as long as we handle dried koji correctly. When using dried koji just make sure to be careful with the water temperature.

Rehydrating dried koji with water is the typical thing to do. But the water amount and soaking time may differ from one brand to another. We recommend reading the explanation on the back of the dried koji packaging to see how long to soak and how much water to add. But in the end, feel free to use your own time and water preference to rehydrate your dried koji.

Recommended Products For Dried Koji