Thinking fermentation is intimidating? Try making this homemade Shio Koji! This traditional Japanese fermented condiment is used as a salt substitute. It's so simple to make and requires only three ingredients: rice koji, salt, and water. Thanks to active enzymes, shio koji is a powerful flavor enhancer that boosts umami and sweetness, and naturally tenderizes proteins. Its savory, salty umami makes a perfect low-sodium salt replacement for everyday cooking.
If you're new to the world of koji fermentation, check out my beginner's guide to what koji is and how to use it! I explained all the tips you need to know and how the beautiful magic of koji elevates an everyday meal!
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What is Shio Koji?
Shio koji, or salt koji, is a savory and salty Japanese fermented seasoning made from rice koji, salt, and water. It's rich in natural enzymes that enhance umami and sweetness in foods and tenderize proteins like meat and fish. Shio koji is a versatile condiment you can use as a marinade for proteins, a seasoning for soups and salad dressings, or a salt substitute to boost umami in everyday meals.
Why You Should Make Shio Koji at Home?
I know you can get premade shio koji, and they're so convenient when you want to jump right into cooking. But nothing beats homemade, and I still recommend making it yourself. So here's why!
Easy to make at home
I know fermentation can feel intimidating. But making shio koji is one of the easiest projects you can try! You only need three ingredients: rice koji, salt, and water. And daily mixing is all you need to do. Salt prevents harmful bacteria from growing!
Cost Effective
Premade shio koji usually comes in small plastic pouches or bottles and can be pricy. By buying rice koji in bulk, you can make large batches at home for a fraction of the price!
Active Enzyme for More Umami
A study published in the Journal of the Brewing Society of Japan found that some commercial brands actually lacked enzyme activity! Scientists believe this is often due to the pasteurization process or other intensive production processes.
On the other hand, your homemade shio koji is full of beneficial enzymes, creating umami and tenderizing foods! Research on shio koji at the Japan Society of Cookery Science shows that this enzymatic activity remains even after one month in the refrigerator, ensuring your last spoonful is just as powerful as the first!
Ingredients for Shio Koji
To make traditional shio koji, you'll need the following ingredients:
- 100g koji rice
- 35g salt
- 130 ml water
You can use regular white rice koji or brown rice koji, which adds a rich, nutty flavor to your shio koji.
Use high-quality sea salt for the best flavor. My favorite is Celtic Sea Salt and Redmond Real Salt.
Salt Concentration in Shio Koji
Salt concentration is calculated as salt weight ÷ total weight(rice koji + salt + water).
Let's use my recipe as an example. The weight of the salt is 35g, and the total weight is 265g. So the salt concentration of this recipe is 35 ÷ 265 = 13.2%.
Let's say it's roughly 13% salt concentration. On average, premade ones on the market are around 11%. If you wish to make reduced-salt shio koji, you totally can!
But keep in mind that salt inhibits the growth of spoilage bacteria. I recommend keeping it above 10%. Using a salt concentration of 10% or more helps prevent the growth of foodborne bacteria, supporting a safer fermentation process.
My recipe is slightly saltier than commercial shio koji to prevent spoilage at home for beginners. It also allows for extra water needed when the dried koji expands on the 2nd day of fermentation.
How to Make Shio Koji: Step by Step
- If the rice koji comes in chunks or blocks, break them apart into individual grains. In a clean jar, combine koji rice and salt. Use a clean spoon to mix well.
- Add water and thoroughly mix. Loosely cover and let it ferment at room temperature for 1-2 weeks, stirring once a day.
- After a few hours or by the next day, the dried koji will absorb the water and expand. If the grains are not submerged in the liquid, add a splash of water until they are just covered.
- Mix the mixture daily. When it starts to smell sweet and fruity, and the rice grains are soft, it's ready. Enjoy adding to your favorite recipes! Transfer the finished shio koji in fridge to store.
Tips for Success
- It takes about 1 week during summer, or when the room temperature is warm. And let it ferment up to about 2 weeks during winter or when the room temperature is cold.
- Keep thelid loose to let the koji breathe.
- The surface can collect bad mold due to oxygen. Mix the mixture daily prevent spoilage.
- Salt can sink to the bottom. Mix well daily to even out the salt. It also prevents bad mold from growing.
- To keep beneficial enzymes active, ensure the wateryou're using is not hotter than 60°C/140°F.
- Dried koji will expand after rehydration. For easy mixing, use a large enough jar that the koji mixture fills up to about half full. If rice koji is not submerged in the liquid, add a splash of water and mix well to prevent spoilage bacteria from growing on the surface.
How to Know When Shio Koji is Ready
The fermentation process usually takes 7 to 10 days at room temperature (around 20-25°C or 68-77°F). In the summer, it may be ready in as little as 5 days, while winter batches might need the full 10-14 days.
Shio koji is ready when rice koji grains are soft enough to squish easily between your fingers, and the mixture smells fruity and slightly sweet (like a banana or chestnuts!)
It might be confusing for beginners, so let me show you how my shio koji matured!
From Day 1 to Day 4
The first few days are where most drastic change happens. Dried koji soaked up the water and became plump.
Sometimes, koji grains soak up so much that they become exposed to the air(see How to Make Shio Koji: Step by Step section for the image). If this happens, add a splash of water to cover them. Use just enough water to avoid diluting the mixture too much.
As it ferments, the grains get softer and are broken down into smaller pieces.
From Day 5 to the Last Day
At this stage, change is not as drastic, but the enzymes are working hard inside! The color shifts from bright white to a creamy yellow-ish white, and the texture becomes like thick porridge.
Signs your Shio Koji is ready:
- The grains are soft to the center.
- Smells fruity, slightly sweet.
- The texture is slightly thick, creamy, and porridge-like.
- Taste slightly sweet.
- There might be small bubbles.
I let this shio koji ferment until Day 11 (it was winter) until the mixture gets creamy. The easiest cue for me was the aroma. This shio koji starts to smell sweet like amazake!
How to Use Shio Koji in Your Kitchen
The beauty of this shio koji is that it enhances the natural flavor of your ingredients. Unlike other seasonings like mayo or ketchup that add their own unique flavor, shio koji doesn't make things taste like "shio koji." Instead, its enzymes react with the foods to bring out a savory umami and sweetness, creating a better version of itself. Because of this, you can use it every day without getting tired of it.
How to Use Shio Koji as Marinade
Most people find that a 1% salt concentration tastes best as it's close to our body's natural salinity. Since this homemade shio koji is roughly 13% salt, a good rule of thumb is to use 10% of the weight of your ingredients (about 1/10th). For example, if you are marinating 300g of tofu, use 30g of shio koji!
1 Tablespoon of Shio Koji is 20g. So for every 1 lb (454g) of food, add about 2 tablespoons of shio koji.
I recommend letting your food marinate in the refrigerator for 30-60 minutes for the tenderizing effect. This resting time allows the enzymes in the shio koji to break down the proteins, resulting in a much softer texture. If you're in a rush, marinade for 15 minutes. It will still do the job! You can also leave it marinating overnight in the fridgeto develop the deep flavor.
Shio Koji Measurement Chart
| Ingredient Weight | Shio Koji (grams) | Shio Koji (Tablespoons) |
| 100g (Small sides) | 10g | ½ Tbsp |
| 200g (For a single dinner) | 20g | 1 Tbsp |
| 454g (1 lb) (Main protein) | 45g | approx. 2 Tbsp |
| 900g (2 lbs) (Batch cooking) | 90g | 4 ½ Tbsp |
This basic seasoning rule works for any ingredients like meat, fish, tofu, and vegetables. This is just a basic recommendation. The saltiness slightly changes depending on the brand or how much water you use. So add more or less shio koji to your taste!
How to Replace Salt with Shio Koji
The simplest way to start using shio koji is to use it in place of regular salt. If replacing salt with shio koji in an existing recipe, you usually don't need the same saltiness. With abundant umami and sweetness, shio koji makes food taste "saltier" and more satisfying than plain salt, perfect for low-sodium cooking.
When replacing, geenral recommendation is using 2 teaspoons of shio koji for every 1 teaspoon of salt called for in a recipe, which is double in volume.
Even though you are using more volume, it actually contains 75% less sodium (about ¼ the salt) than pure salt. But still, with the deep umami and complex fermented flavor, you won't miss the extra salt.
Of course, adjust the saltiness to your liking!
Recipe using Shio Koji
Either homemade or store-bought, shio koji is so versatile and easy to use! Here are a few of my favorite ways to use shio koji's irreplaceable flavor.
- Creamy Roasted Tomato Soup with Shio Koji: The shio koji replaces regular salt beautifully, enhancing savory umami and making the sun-kissed tomatoes taste even richer and sweeter.
- Marinade: Marinade fish, chicken, and pork, and refrigerate overnight in the fridge. Grilling the next day makes an easy weekday dinner.
- Asazuke(Japanese Quick Pickle):
- Deepen Your Knowledge: Curious how koji makes food taste better? Make sure to check out my What is Koji? post explaining the culinary magic behind koji.
Golden Rules of Seasoning with Shio Koji
For Shio Koji Marinade
- Add 10% of the weight of your ingredients.
- 1 tablespoon of Shio Koji is 20g.
- Add 2 tablespoons of shio koji for every 1 lb (454g).
- Refrigerate for 30 min to tenderize. Up to overnight for deep flavor.
When Replacing Salt with Shio Koji
- Replace 1 teaspoon of salt with 2 teaspoons of shio koji (double in volume).
- This is not a 1:1 salt replacement! 2 teaspoon of shio koji contains 75% less sodium than 1 teaspoon of pure salt.
- With complex umami, shio koji makes food taste "saltier" and more satisfying, making it perfect for low-sodium cooking.
The conversion ratio for shio koji to salt is 2:1 by volume, which reduces total sodium by approximately 75% while maintaining flavor through fermentation-derived umami.
Storage
While the science shows enzymes stay active for at least a month, your shio koji can actually last longer if handled properly. I recommend using it within 6 months in the refrigerator. Or you can freeze up to 1 year.
- Sight: It should be a creamy white or pale light-yellow color. If you see pink, green, or black fuzzy mold, discard the whole jar. (Note: A little liquid separation on top is normal, just stir it back in!)
- Smell: It should have a pleasant, sweet, and slightly fruity aroma (similar to sake or amazake). If it smells sour, rancid, or 'off' like old gym socks, it's time to toss it.
- Taste: It should be salty and sweet with a deep savory (umami) finish.
Shio koji will slowly continue to ferment in the refrigerator. So it matures and develops a mellow flavor over time. Freezing, on the other hand, stops the fermentation process, so that you can preserve the fresh flavor.
Shio Koji FAQs
While fermentation slowly continues, shio koji will stay delicious in the refrigerator for up to 6 months. For longer storage, you can freeze it up to 1 year to stop the fermentation process entirely.
As a general rule, use two teaspoons of shio koji for every one teaspoon of salt called for in a recipe. Two teaspoons of shio koji actually contains 75% less sodium (about ¼ the salt) than pure salt. But the deep umami and complex fermented flavor make up the salt.
How to Make Shio Koji
Ingredients
- 100 g koji rice
- 35 g salt
- 130 ml water more as needed
Instructions
- If the rice koji comes in chunks or blocks, break them apart into individual grains. In a clean jar, combine koji rice and salt. Use a clean spoon to mix well.
- Add water and thoroughly mix. Loosely cover and let it ferment at room temperature for 1-2 weeks, stirring once a day.
- After a few hours or by the next day, the dried koji will absorb the water and expand. If the grains are not submerged in the liquid, add a splash of water until they are just covered.
- Mix the mixture daily. When it starts to smell sweet and fruity, and the rice grains are soft, it's ready. Enjoy adding to your favorite recipes!
- Store shio koji in the refregeator.
Notes
- The grains are soft to the center.
- Smells fruity, slightly sweet.
- The texture is slightly thick, creamy, and porridge-like.
- Taste slightly sweet.
- There might be small bubbles.
- Add 10% of the weight of your ingredients.
- 1 tablespoon of Shio Koji is 20g.
- Add 2 tablespoons of shio koji for every 1 lb (454g).
- Refrigerate for 30 min to tenderize. Up to overnight for deep flavor.
- Replace 1 teaspoon of salt with 2 teaspoons of shio koji (double in volume).
- This is not a 1:1 salt replacement! 2 teaspoon of shio koji contains 75% less sodium than 1 teaspoon of pure salt.
- With complex umami, shio koji makes food taste "saltier" and more satisfying, making it perfect for low-sodium cooking.
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