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The Japanese Cooking Guide; Koji Rice

the Japanese cooking guide, shio koji, koji rice Food & Recipes
Food & Recipes
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To tenderize meats and get rid of the fishy flavor from fish, Japanese cooking often use “Shio Koji”.

“Shio Koji”, which I am talking about today, is the interesting fermented condiment and when you hear about “fermented food”, you can’t ignore its tremendous benefits.

Japanese culture and fermented food have been related for a long long time, Miso paste, soy sauce, Mirin, Sake…These are made from Koji.

I am one of the cooking lovers who have been obsessed with Shio koji marinating.

Today, I am going to tell you about the ultimate guide of “Shio Koji”.

What’s Koji???

koji, soy sauce

Simply, “Koji”(麹) is the moldy steamed grains such as barley, rice, and beans propagated “Aspergillus oryzae”.

“Aspergillus oryzae” is a type of mold known as kōji mold (Japanese: ニホンコウジカビ (日本麹菌), is essential for the fermentation and aging of miso, soy sauce, and Japanese sake, and has been certified as a bacterium representing Japan.

Koji has long been rooted in Japanese food culture and has contributed to the development of Japanese food aesthetic.

I’m sure you might think that when they hear mold, “Eh? Is that safe?”

Of course, koji molds in those beneficial molds,
in other words, koji is a fermented food.

Koji contains many enzymes such as Proteolytic enzyme (protease) and starch degrading enzyme (amylase).

  • Protease → decomposes protein into amino acids → Umami, source of savory flavor.
  • Amylase → Decompose starch into glucose → Sweet
  • Lipase →breaks down fat into fatty acids and glycerin →Reduce greacy taste

By the action of these enzymes, the meat is tenderized with better taste.

Koji-Rice = Shio-Koji

Koji-Rice is called “Shio-Koji” (塩麹) in Japanese, literally means Salted Koji Rice.

“Shio-koji” is one of the fermented seasonings, “Shio” means “Salt” in Japanese, as the name implies, it is a seasoning made from salt and koji.
There are many seasonings made from koji, such as miso and soy sauce. So Koji-Rice is the koji made of rice.

In 2011, the “Shio-koji fad” occurred in Japan, and there have been many cooking recipes of Shio Koji produced since then.

Shio-koji is a mixture of salt and koji, it is salty, but there are the umami and sweet tastes produced by fermentation.
Therefore, it can be substituted salt or soy sauce to reduce salt for cooking, bring out the umami of food, and can be used as a sauce. It is a versatile seasoning.

How To Marinate Meat With Shio Koji

marinate pork with sio koji

The most major usage of Shio Koji is as a tenderizer for meat and fish.

Just marinate any kind of meat with shio-koji.

I always marinate pork chops for Japanese cutlet with shio koji and freeze them.

You will be very impressed how much tender they are!

Sometimes pork loin chops get dried even when cooked perfectly, but shio koji marinade really works to keep moist and juicy, moreover, it gives Umami flavor.

You may need to take some time to get used to the “koji” flavor. (So did I.), but my American husband doesn’t say anything about the hidden flavor (fruity? yeasty? funky sweet?) and love my Japanese pork cutlet, so should be acceptable taste to you too.

(But marinating with shio koji is actually secret for him because he will be scared and not try it anymore.)

When you marinate fish with shio koji, it helps to get rid of fishy flavor from them.

If you care about the unique taste, rinse off or wipe off shio-koji.

Avoid applying shio-koji too much, use it for approximately 10% of the weight of the meat.

Marinated time depends on the type and thickness of food

arinade chicken and shio koji and freeze them

It depends on how thick the meat, but if you marinate it for about 30 minutes, it will be tender enough.

For fish, over 30 minutes to overnight.

But, when the meat or fish is marinated for too long, Koji’s power is really strong, so it can break down food too much or get too salty.

For sashimi fish, lightly apply shio koji for only 10 minutes.

Because the shio-koji pause its enzyme working in the freezer, so you can marinate meat and freeze it. Besides, in this way, it prevents getting food too salty.

Koji Health Benefits

The fermented food, Shio-Koji, is not only helping tenderize food by decomposing the raw materials but also very nutritious such as lactic acid and vitamins (B1, B2, B6, pantothenic acid, biotin (vitamin H), etc.

It also contains more nutrients than salt alone. These are considered to have the effect of increasing the metabolism of the brain and the effect of recovering from fatigue.

  • Improve bloodstream to lower blood pressure and prevent lifestyle-related diseases such as arteriosclerosis.
  • Controls cholesterol and neutral fat levels to prevent swelling and lifestyle-related diseases.
  • Stimulate brain activity to prevent dementia.
  • Help promote healthy gut bacteria
  • Boost recovery of mental and physical recovery and enhances the immunity system.
  • Relax mind and body, relieve stress, and promote good sleep.
  • Help to produce collagen and keep the skin moist.
Calories380 kcal
Protein7.7 g
Total Fat1.4 g
Carbohydrates84.1 g
Source; Isesou Miyako Koji

How To Make Koji Rice (Shio-Koji)???

shio koji

You can find “Koji” easily online, which I always do. (I live in the area where don’t have an oriental grocery store close by.)

how to make shio koji, 3

Salt is the key to make good koji rice, so use natural mineral salt such as sea salt. I use Himalayan pink salt. Avoid table salt.

Koji RiceSalt
100g3.5oz30g2 tbsp
200g7oz60g4 tbsp
300g10.5oz90g6 tbsp

Also, use mineral soft water.

Thoroughly clean and sterilize the container before use and allow it to dry before use. It is better to choose a see-through container so that you can check the fermentation status.

If you have a lump of koji rice, please make it into grains and mix with salt evenly. Please note that salt or koji may rot if the salt is not spread all over the koji rice.

Since gas is generated, do not close a lid tight. It is also good to use cheesecloth instead of the lid.

Stir the koji rice once a day. Fermentation becomes uniform, so you can get good shio koji.

If the koji absorbs water and the water level goes down, add water each time. Add just enough water until the koji is covered. If adding water is too much, the salt concentration will decrease, causing decay and discoloration.

Generally, the fermentation will be completed in 10 to 14 days, but it may be slower when the temperature is below 20 degrees Celsius (68F). When the rice grains are very soft and it looks like porridge, it is a sign to finish.

You can’t wait???

Here’s already-to-use products online.

The perfect big size for plenty of use. Reduced 20% sodium content. This product with the protease (proteolytic enzyme) activity increased. It makes meat and fish tender and flavorful.

This is a liquid type of Shio Koji, so you don’t have to be hesitant to use it rather than porridge-looking koji-rice. Because of the clear-brown liquid, it doesn’t bother the natural color and texture of ingredients. Just use like regular koji rice. Also, lower sodium products. Gluten-Free.


shio koji

Koji Rice (Shio Koji)

The Japanese fermented seasoning used to tenderize, marinate, and bring rich umami flavor.
Cuisine Japanese


  • 200 grams Koji (about 7 oz)
  • 300-400 cc Water (1.2-1.7 cups)
  • 60 grams Salt (1/4 cup)


  • Mix really well with Koji and salt.
  • Cover Koji & salt with just enough water. Mix well.
  • Transfer to the clean container and put the lid on but don't fasten.
  • Allow it in the room temperature for 10 - 14 days until rice grain becomes soften, loses its shape, and smells sweet like bananas. (Keep away from direct sunlight.)
  • *Mix koji rice every day, add water when the water level gets below.



  • The best salinity ratio of koji rice is between 30% and 35%. You may want to reduce the amount of salt, but it causes decay and odor due to its low sodium.
  • Mix koji rice and salt evenly. Otherwise, there is a risk that the koji rice will rot.
  • Add water until the koji rice is just covered. (Not too much, not too little). Koji absorbs water, so check the water level every day. Add water accordingly.
  • The fermentation period is about 10-14 days at room temperature.
    If koji rice is stored in a place with a low temperature (below 68F), fermentation will slow down and it will take 14 days or more for the salt koji to mature. On the other hand, if the room temperature is higher, the fermentation speed is less than 10 days. 
Keyword condiment, Seasoning

How To Keep IT?

In The Refrigerator

Shio Koji will be last in the refrigerator for about 6 months.

Use a clean spoon to scoop every time, and do not leave it in the container.

In The Freezer

You can freeze koji rice, and it won’t be frozen completely.

It is still soft so it can be used without thaw completely.

Fermentation can be stopped in a freezer. However, the flavor will gradually be lost, so you should use it within 6 months.

When shio koji is repeatedly frozen and thawed, the deterioration rate will increase. Make small batches if you think you don’t use much one time.

Read Next…

I am obsessed with this Japanese traditional fermented condiment, besides, I have tried many ways to make the meat tender and change tenderize methods for each dish.

Koji rice = shio Koji are compatible with especially pork, chicken and fish.

When I don’t want to give any flavor, I use “the baking powder” solution.

If you are interested how I make meat tender with other ways, please read next here!

the Japanese cooking guide, shio koji, koji rice

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