Koji & Miso

How to make Shio Koji

A savoury Japanese seasoning of rice koji, salt, and water, fermented into a sweet-salty paste that tenderises and adds umami. Expect a few minutes of work, then 7-10 days of daily stirring, with the koji softening as the sign it is ready.

Quick answer

Combine the koji, salt, and water in a jar and cover it loosely. After 1 day, stir daily for 7-10 days until the koji softens and smells sweet. After 10 days, blend the paste smooth if you like, then refrigerate it.

Difficulty
Beginner
Total time
10 days
Ingredients
3
Steps
3

Safety

  • • Use the full measured salt, which is the main control that keeps shio koji safe.
  • • Keep the koji covered with liquid and top up the water as it absorbs it.
  • • Stir daily so the koji ferments evenly.
  • • A sweet, savoury smell is normal. A rotten or off smell means the batch should be discarded.

Step-by-step

Day 0

Step 1: Mix

Combine the koji, salt, and water in a jar and cover it loosely.

  • Set up clean equipment Wash the jar and spoon before you start.
  • Combine koji, salt, and water Mix the koji with the salt, then add water to cover.
Day 1

Step 2: Ferment

Stir daily for 7-10 days until the koji softens and smells sweet.

  • Stir daily Stir once a day and top up the water if the koji pokes out.
  • Check readiness It is ready when the koji is soft and smells sweet and mellow.
Day 10

Step 3: Blend and store

Blend the paste smooth if you like, then refrigerate it.

  • Blend and refrigerate Blend for a smooth seasoning, then chill.

What to look for

  • • Day 1-2: The mix is cloudy and salty with firm, separate koji grains. From here the koji slowly softens and sweetens.
  • • Day 4-6: The koji is softening and the smell turns sweet and a little fruity. That is the enzymes breaking the rice down into sugars and umami.
  • • Day 7-10: The grains mash easily and the paste is loose and porridge-like. That softness means the shio koji is ready to use.

Troubleshooting

  • The koji rises above the liquid. It absorbed the water as it swelled. Stir it down and add a splash more water to keep it just covered.
  • It is not softening or sweetening. The room is cool, so the ferment is slow. Move it somewhere warmer and give it a few more days, stirring daily.
  • It tastes very salty on its own. That is normal for shio koji, which is a concentrated seasoning. Use it in small amounts to season or marinate food rather than eating it straight.

Storage

Refrigerate the finished shio koji in a sealed jar, which slows the fermentation to a crawl.

Shelf life: about 3-6 months refrigerated

Serving suggestions

  • • Rub it onto meat or fish before cooking to tenderise and add umami.
  • • Toss it through vegetables before roasting.
  • • Whisk it into dressings, marinades, and dips in place of salt.

See the full recipe — free

Enter your email to unlock every step, the full timeline, and the troubleshooting guide. Unlocks all 47 recipes.

Frequently asked questions

What is Shio Koji?

A savoury Japanese seasoning of rice koji, salt, and water, fermented into a sweet-salty paste that tenderises and adds umami. Expect a few minutes of work, then 7-10 days of daily stirring, with the koji softening as the sign it is ready.

How long does it take to make Shio Koji?

Most batches of Shio Koji are ready in about 10 days, though exact timing depends on temperature and how the ferment tastes along the way.

Is Shio Koji hard to make?

Shio Koji is a great beginner project — no special skills required, just clean equipment and a little patience.

What do you need to make Shio Koji?

You'll need Rice koji, Sea salt, Filtered water.

How do I know when Shio Koji is ready?

Watch for these cues: Day 1-2: The mix is cloudy and salty with firm, separate koji grains.; Day 4-6: The koji is softening and the smell turns sweet and a little fruity.; Day 7-10: The grains mash easily and the paste is loose and porridge-like..

How do I store Shio Koji?

Refrigerate the finished shio koji in a sealed jar, which slows the fermentation to a crawl. Shelf life: about 3-6 months refrigerated.

Related fermentation recipes

Koji & Miso

Miso

A savoury fermented paste of soybeans, rice koji, and salt, aged slowly into deep umami. Plan on an overnight soak and a few hours of cooking and mixing, then 6-12 months of patient fermentation, tasting from around six months to decide when it is ready.

180 days · Intermediate · 3 ingredients