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How To Make Soy Sauce At Home (Shoyu) With Koji - Through Fermentation

Updated: Jul 25, 2023

Soy sauce in first stage of fermentation at Tiki Food Lab made with heirloom grains and PH balanced water

What is the history of Soy Sauce, Tamari and Miso?

Soy sauce (also called Shoyu - which is Japanese soy sauce) is delicious and extremely useful to build your umami pallet. At our restaurant, Suis Generis, we use soy sauce to marinate, baste, and as an ingredient to numerous sauces, glazes and emulsions.

The forefather of soy sauce was "Jan," which originated in China as a fermented sauce derived from meats, vegetables and seaweed. Not long after the advent of "Jan" a sauce in Japan called "Hishio" came into existence. It was a type of hybrid of modern soy sauce and miso, with less water than modern soy sauce. An interesting aspect of making miso is that tamari forms at the surface if your miso mixture has a high water content. The liquid that forms on the surface of miso is called "Damari" - and is thought to be the origin of the word "Tamari." The difference between soy sauce and tamari is wheat, which is added to soy sauce, but not to tamari.

At the Tiki Food Lab, we purposefully make our misos with high water content to later harvest tamari from the surface. We combine the various tamari harvests into one container that becomes our house tamari - and is more complex than any tamari you would normally taste. Of course, that is because our misos are also very unusual, made with ingredients such as charred brussels sprouts, corn, smoked pineapple, king cake, coffee, strawberry tree fruit, figs, artichokes, duck weed, and many other ingredients!!

For more information on the history of soy sauce, scroll down the the Research Sources section at the end of this blog entry.

Tiki Food Lab Soy Sauce - Duck Weed is an untapped ingredient!

What Are The Ingredients Of Traditional Soy Sauce?

Traditional soy sauce is made with five ingredients: soybeans, koji, water, wheat and Salt. Koji is where the magic comes from! Koji is rice that has been inoculated with a spore called Aspergillus Oryzae, which originated on ears of rice and was found by accident to have preservative properties several thousand years ago in China! It is truly one of the original forms of alchemy.

What Type Of Koji Do I Need To Make Homemade Soy Sauce?

Koji is the catalyst to make shoyu, miso and sake - similar to yeast being the catalyst for bread. The beauty of Koji is you can get it easily by purchasing a pre-packaged dried version on line (such as from Amazon or from Rhapsody Organic). This is the easy method. At the Tiki Food Lab, we like to make fermentation accessible to everyone. So, this option is a good way to start. The thing is, for any recipe using dry koji, you need to adjust the water content upwards to re-hydrate the rice grains.

Ultimately, growing your own koji, from koji spores, will produce a more refined product with additional complexities of flavor. However, from our test trials, while the differences are there - and matter for high end culinary applications, they do not really matter if you want to make soy sauce, miso, amino sauces, or other koji-related ferments at home.

We will post blogs on how to make a fermentation chamber and how to make koji directly from Asppergillus Oryzae spores (also called koji starter) so you can also get into that! There are even different types of Oryzae spores that produce varying flavors and you can grow it on an array of substrates to further differentiate your end result. Also, you can use koji to make shio koji and shoyu koji. However, for now, lets keep it simple!

How To Make Soy Sauce At Home:

Lets take it from the top to make your own soy sauce! The basic recipe for making soy sauce is as follows:

  • One part koji - If you are feeling frisky, grow your own. However, for an easy entry into soy sauce making, buy dry koji and use that.

  • 1 part protean - We use 50% soy beans and 50% wheat (whether you want to make dark soy sauce which is typically thicker with less water content, or light soy sauce, the key is - you need soybean and wheat). Remember, wheat is a key ingredient for soy sauce. Alternatively, if you use all soy beans for your protean, you will be making Tamari. For variations, you can use other combinations such as 50% soy beans, 45% wheat and 5% mudrooms or any other flavoring ingredient. In general, high protean vegetables such as green peas, spinach, sweet corn, brussels sprouts, broccoli, kale, mushrooms, sweet potato and avocado work best.

  • 2 parts water - Use good quality water because it matters. Never use tap water because it usually contains chlorine, fluorides or other chemicals that inhibit fermentation.

  • Salt in the range of 8-16% - Once again, the ingredients to make your salt water matter! Never use iodized salt because it also inhibits fermentation. You can use kosher salt, or sea salt, or better yet, use tasty exotic salts like Himalayan pink, French grey sea salt or Hawaiian Alaea salt.

Preparing The Ingredients To Make Soy Sauce (Shoyu):

Soak your soybeans over night. It is best to use the mature tan soy beans instead of the young green ones. Also, buy organic if possible - always remember the quality of the ingredients matter. Rinse and boil the soybeans until they are tender but not falling apart. The time varies widely - but they often take 2-4 hours to cook. You can also use a pressure cooker, which will reduce your time to about an hour or less.

Select your wheat. You will see some recipes using flour, but stay away from that. Most flour purchased in grocery stores is stale and flavorless. Instead, use whole wheatberries - or get crazy and buy spelt, yecora rojo, or other heirloom variety such as fife, pima club or rogue de Bordeaux. We buy our wheatberries from:

Toast your wheat. You can do this in a dry pan, under a broiler, or even better in a BBQ grill to get some smoke flavor. Experiment with all options! We find the easiest method is to simply heat them in a dry pan while constantly tossing them. Once they start to pop, crackle and turn slightly brown - they are ready.

Make sure your grains and soybeans are no warmer than 110 degrees, then it's time to do some mixing! However, before we get to that - a note on weighing ingredients. You need a good scale, and preferably one that gets down to the graham or hundredth of an ounce. Measure all of your ingredients to achieve the weight ratios discussed above.

Three Soy Sauce Trials at the Tiki Food Lab

Once you have set aside your 1 part Koji, 1 part protean (including both the wheat and the soy beans) and 2 parts water, you are ready to take the total weight of all of those ingredients and add your salt. For a 6 month aged soy sauce, you can generally stay in the 8-10% range. If you want to go for a 1 year + ferment, you may want to be more in the 12-16% range. However, if you go 6 months at a lower percentage, you can always add more and go longer. Don't be afraid to experiment. Your ferment will let you know if something went wrong. However, Koji is the magic that protects you from harmful bacteria. Of course, you always should observe and proceed with caution with any ferment. Trust your eyes and nose. If it doesn't smell right - it probably is not right. Koji makes things smell like passionfruit flowers, which is a beautiful thing.

After you measure the appropriate amount of salt, mix it into the other ingredients and then run the whole thing through a Vitamix or food processor. You want to crack your grains some so the Koji can access the proteins. Alternatively, you can run your grains trough a mill before combining - but most people don't have a Food Lab and grain mills just hanging about - so we try to include information in our blogs to make the process accessible.

It helps to use a food processor or Vitamix to pulse your ingredients - allowing koji access to the "food"

Starting The Soy Sauce Fermentation Process - Seeking Umami:

First things first. Don't be scared! Remember, Koji can out compete almost any bad bacteria. Get a clean glass container with enough room to have several inches at the top. We like clear glass because you can see what is going on inside. Remember - trust your eyes and nose! After you blend everything, carefully pour it into your container. You can cover with a hard lid or cheesecloth affixed with a rubber band. Both methods work - but using the cheesecloth results in a more concentrated finished product due to ambient evaporation. You will be leaving this at ambient temperature, so keeping fruit flies and critters out is key.

Here is the key - stir your soy sauce twice per day for the first 3 months an then daily for the next 3 months. After that, you can mix 2-3 times per week - depending upon your room temperature. If you miss a mixing time (or 5) don't worry, just stir it and monitor. If anything it may build a small amount of alcohol if it is not getting sufficiently oxygenated. We actually experiment with less mixing to play with the ultimate result. Sometimes you just want to make soy sauce vinegar - but we will save that for another day.

Feel free to try your mixture regularly to see how you like it. Once it tastes good - start using some an keep fermenting.

When you get the taste you want, strain it out (and save your strainings to make a Jang - also to be saved for another day!). At this point you hopefully have good soy sauce - and you can decide if you have finished soy sauce, or if you want to pasteurize it to keep longer.

At Suis Generis Restaurant and the Tiki Food Lab - our goal is to achieve zero waste, so using the by-products of fermentation and cooking is an essential part of our process.

Contact us to schedule your private chef curated tasting menu, cooking/fermentation class, or sign up for one of the Food Experiences already scheduled!

Additional Research Sources:



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