Impress your friends and save money by making your own soy sauce from scratch. Today we’ll learn how to make a homemade shoyu, a fermented soy sauce made from soybeans and wheat berries.
This post has been in the making for several years now. Yes, years!
I’ve had several failed attempts before finally reaching success and making a wonderful soy sauce with complex flavors. Fortunately, my failures were due to misinformation more than they were to a complicated process. Making your own soy sauce does require some patience, but it really isn’t that difficult.
When I first started trying to make my own soy sauce, there wasn’t a lot of information on the web, and the only posts about the process showed people making patties out of soy and letting them grow mold from whatever wild molds might be present in the air. Many of these “recipes” were based on people watching their Asian relatives make soy sauce at home. I guess the whole process sounded a bit risky, but since it’s quite common for people to make sourdough starters from the wild yeasts in the air, I thought the idea had some merit and decided to give it a try. (I mean soy sauce making had to start somewhere, right?)
The problem?
Making soy sauce is a long process, and each time you give it a failed shot, you end up wasting a lot of time.
I tried making a homemade soy sauce with local wild molds, and while trying it didn’t kill me, it didn’t impress me either. Maybe it has something to do with the fact that the wild molds and yeasts here in Spain are different than those in the soy sauce making regions of Asia. (From a bit of further research, it appears that making soy patties that collect local molds is most typical in Korean soy sauce making.)
The process of making it wasn’t easy sailing either. I had to endure foul-smelling moldy soy patties (not to mention my husband’s complaints about the odor.)
We’ll just say that my first homemade soy sauce wasn’t good enough to share on the blog. Just as sourdough starters will vary from region to region, not only can a wildly propagated soy sauce have a lot of variances, but it could be potentially dangerous. That’s why you need to start with a specific fungus for inoculating your batch. Luckily, using a starter fungus also makes for a much more pleasant soy sauce making experience. (Yes, it smells much better too!)
Watch How to Make Soy Sauce (Homemade Shoyu)
What is Soy Sauce?
Soy sauce is a thin, liquidy, Asian condiment normally made from fermented soybeans. Specific strains of fungus are grown on soybeans, and then the mixture of fermented soybeans is allowed to continue to ferment within a salt brine.
Soy sauce varieties vary from region to region, and not all modern day soy sauces are actually even fermented anymore. Most store-bought soy sauce will be pasteurized, too, so it’s great to be able to make your own and add one more unpasteurized fermented food to your pantry. (Plus, if you use a lot of soy sauce, you can save a lot of money with this one!)
What is Shoyu?
Shoyu is the Japanese term for the type of soy sauce that is made with both soybeans and wheat. It is normally what we are used to seeing when we think of “normal” soy sauce.
Shoyu differs from Tamari, another type of soy sauce, in that tamari uses little to no wheat and is sometimes fermented with a different strain of fungus (Aspergillus tamari). Tamari began as a byproduct of making soybean miso. It was the liquid that pooled up on the miso. Nowadays, though, with an increased demand for a wheat free soy sauce, companies work to make more tamari as a stand-alone product.
Is Soy Sauce Vegan?
People often ask this question, and the answer is Yes! Soy sauce is vegan.
Soy Sauce Ingredients
Soy sauce only uses soybeans, wheat, salt, water, and the strain of fungus desired for fermentation, normally Aspergillus oryzae or Aspergillus sojae. Aspergillus tamarii is sometimes used for making tamari.
On my very first attempt at making soy sauce, I went to the health food store and bought the only soybeans that were for sale at that particular store. They were small, green soybeans and didn’t make as nice of a paste or sauce.
I later saw that you could buy either larger white (beige) soybeans or the tiny green ones. It turns out that the beige soybeans are more mature soybeans, and the green soybeans are younger. The mature soybeans are the ones that are normally used to make everything from soy milk to, well, soy sauce.
How is Soy Sauce Made?
Homemade Soy Sauce (Shoyu)
Makes around 1 gallon
Ingredients
- 1200 g dry soybeans (the white or beige type)
- 1200 g wheat berries Soft wheat gives better flavor than hard wheat
- 7.5 g aspergillus orzyae starter meant for shoyu
For the Brine
- 825 g sea salt
- 3.8 liters water
Instructions
Prepare the soybeans
- Rinse the soybeans and cover them with water in a large glass jar or another suitable container. Keep in mind that they will double in size when they absorb the water.
- Soak them overnight, or for 12- 16 hours. (Add more water, as needed, to allow them to fully hydrate.) Notice in the photo that they have doubled in size once hydrated.
- Drain the soybeans and cook them by steaming them in a pressure cooker for an hour and a half, or cook them in boiling water for around 6 hours. A slow cooker is a good option in that case.
I used a pressure cooker and poured water in the bottom of the pressure cooker. I then put a stainless steel steamer basket over the water and filled the basket with the soaked soybeans. I set the pressure cooker to cook for an hour and a half. - When fully cooked, you should be able to easily crush the soybeans with your fingers.
Prepare the wheat
- Brown the wheat berries in a skillet for several minutes until they turn golden brown. You can also broil them in the oven, spread over a baking sheet, stirring every couple of minutes to prevent burning, if you prefer.
- Grind the wheat coarsely using a food processor, grain mill, or another type of grinder. You are aiming to break each grain into several pieces. You don’t need to completely pulverize the wheat berries into powder.
Preparing the koji
- Mix together the ground wheat berries and the cooked, drained soybeans in a large mixing bowl. Allow the mixture to cool.
- Sprinkle a koji starter over the wheat and soy mixture and thoroughly incorporate it into the mixture.
- Spread the inoculated mixture over glass or stainless steel trays or bowls. (Use something with a broad base so that you can spread out the shoyu koji.)
Make furrows (small valleys) in the mixture every 2 inches or so to avoid having thick layers where hot spots emerge. (Hot spots are areas where the mold gives off too much heat.) - Place a thermometer in the koji and cover the trays with either a plastic wrap or a tight weave cloth to help keep the moisture inside. Incubate the trays at around 85ªF (32ºC). (I used my oven with the oven light on to keep the temperature slightly elevated. You can also use hot water bottles or ice cold water bottles under the trays in an ice chest to raise or lower the temperature as needed.)
- Check the koji temperature every few hours to make sure it is staying in the 80-95ºF (27-35ºC) range. If the temperature gets too high for too long (over 104ºF (40ºC), unwanted bacteria can grow in the koji and spoil it. Each time you check on the koji, stir it, breaking up clumps as needed, and spread it out and add the furrows back in before covering and incubating again.
After 2- 2.5 days
- Continue to monitor the koji for 2 to 2 and a half days. You’ll notice that a fuzzy, soft white mold will cover the koji.
- It’s OK for some areas to begin to turn yellow or even a light yellow-green color. The yellowish green color is the formation of new koji spores. (Discard any koji that has grown black, or dark green mold. You also want to avoid any koji with shiny or sticky spots.)
Prepare the brine solution
- In a large glass container (around 2 gallons), mix together 1 gallon of filtered or spring water with 3.5 cups of sea salt. Stir until the salt has fully dissolved.
Prepare the moromi
- The moromi is the mixture of the koji and brine solution. Stir the koji into the brine solution and cover the mixture with a tight fitting lid. Label it with the date.
- Keep the moromi in a warm spot to continue to ferment. Stir the mixture daily for a week or so. After than, keep it in a warm spot (ideally around 77ºF (25ºC)), stirring it at least once a week for around 6 months.
- After around 6 months, you’ll notice that the color of the moromi will have darkened into a deep rust brown color. It may be either have separated into a liquid and solids (like mine) or be more or a homogenous thicker mixture.
Straining the moromi
- After 6-12 months fermentation, you’ll want to strain the moromi to obtain your homemade shoyu. The easiest way is probably to pour it into a cloth-lined strainer and pour some of the mixture into the strainer. You can then twist the cloth to press the filtered liquid through the cloth into a bottle.
- After around 9 months, around 3 months ago, I strained mine and it was a light, rust-colored liquid that tasted and smelled like soy sauce, but was much lighter in color.
- I was making homemade tamari at the same time (I’ll share that process soon- or as soon as I’m happy with the result), and this shows the 2 bottles I strained out 3 months ago. (I left the rest in the jar to continue fermentation there with the soybean and wheat mixture.)
Obtaining a dark-colored soy sauce
- One thing I had learned from my first failed attempts at making soy sauce was that one of the things that helped achieve a dark-colored soy sauce with complex flavors was to allow the sauce to ferment in the hot sun. So, I placed both bottles (of soy sauce and tamari) out in the hot sun from the end of June until the end of September. I was happy to see that both sauces had darkened with time out in the sun.
- You’ll notice that after 3 months outside in my sunny terrace, not only did they darken, but they also separated slightly leaving a bit of soy residue floating on top of the bottles. I strained the mixtures to obtain my sauces.
- I filtered the soy sauce again through a cloth to remove any soybean residue. The resulting liquid was a wonderfully dark colored shoyu with wonderful flavor.
Notes
What to do with the leftover soybean mash
While some people discard the soybean mash leftover after having strained out the soy sauce, others, like me, use it as they would miso in recipes.
Miso paste can be stirred into other sauces or mayonnaise to add a bit of saltiness and umami. It can be stirred into hot water, especially that boiled with seaweed varieties like kombu and wakame, to make a miso soup. The paste can also be added to stir fries.
Troubleshooting the soy sauce making process
My moromi is forming a mold on top
As a bit of an experiment, I had a separate jar of moromi fermenting that I left undisturbed. If you don’t stir the mixture very often, mold can form on top. After a bit of research, most soy sauce fermenters believed that it is OK to remove the top layer of mold and continue to ferment the sauce below.
In this case, the mold forming had the same colors and scent as the soy koji that I had made in the beginning, so I scraped peeled off the mold (it had a similar texture and held together as the koji had), continued to ferment the soy sauce, stirring occasionally. The resulting sauce didn’t appear any different than the other batch.
Use common sense here. If your moromi forms an unusual mold with a dark color or foul odor, while it may break your heart, you may be best to throw it away.
My moromi is forming a slimy layer
After having scraped off the moldy layer of my experimental batch of homemade soy sauce, I once again left it undisturbed. This time it didn’t form a mold, but instead formed a bit of a slimy layer on top. The top layer didn’t smell unpleasant, but I wasn’t sure I wanted to mix it in with the rest of the batch either.
My best guess is that this is some type of yeast that is forming on top. It gives off a yeast-y beer-like scent. Even though it wasn’t offensive, I scraped off most of the layer and mixed everything together again.
My soy sauce is too light in color
If I had only followed the instructions that came with my shoyu starter, I would have ended up with a dark amber colored soy sauce. In fact, most of my large batch still looks like the bottle above. (I took this picture this week of a bottle that I just strained.)
So, how did I end up getting such a beautifully dark soy sauce as shown in the first picture?
Well, two things help darken the soy sauce.
First, just filtering out any residual soybean paste will leave behind a darker color. After a couple of days, the soybean paste settled to the bottom, making the soy sauce look darker in color. To get it looking even darker, I filtered it through a tightly woven cotton cloth. You can see the huge difference in color already! It takes a bit of patience, but it’s worth the effort.
Second, it appears that one of the secrets to dark soy sauce is the same as the secret to dark skin in the summer… the sun!
The instructions that came with my starter never said anything about exposing the sauce to the sun, but through my earlier experimentation with making soy sauce using wild fungus, I learned that the sun may be your best friend when trying to make a dark, rich homemade soy sauce!
I read several accounts of people remembering their family members making soy sauce in Asia. They talked about the importance of using the sun, even to help prepare the brine for the koji. These people made the salt water ahead of time and allowed it to steep for several days in the sun before adding in the koji. They then proceeded to add the koji and allowed the mixture to ferment in the hot sun!
While I didn’t experiment with doing the whole fermenting process in the sun, I was a bit disappointed with the color of my homemade soy sauce, so I decided to experiment with leaving that outside in my terrace. I wasn’t sure if I’d be hurting the soy sauce, so I only strained out a small bottle and left it in a sunny part of my terrace for several weeks. (Looking at the dates on my photos, it appears that I actually left it there for almost 2 months.)
When it was time to take a look at it again, I was really happy to see how dark it had gotten. So, I’m now sunning out another bottle of soy and am tempted to bring out the whole unstrained batch!
Should you pasteurize your soy sauce?
It is said that pasteurization of the soy sauce will help extend its shelf life, and the cooking of the sauce helps to enhace its flavor and aroma. The idea is that you are killing off the bacteria in the sauce, and also beginning a Maillard reaction to deepen the flavor.
While that seems to be the general consensus, I’m not 100% sure if either of those statements is completely true. I’ve seen home brewers say that they like to leave half of their soy sauce unpasteurized because they think unpasteurized soy sauce has a more complex flavor profile. They pasteurize in the hopes of having their soy sauce last longer.
In a similar bit of skepticism, I really have to wonder if killing off the bacteria in the sauce will really extend its shelf life. When you make something like a homemade sauerkraut, some people say that the beneficial lactic acid bacteria that form also help preserve it. In fact, Leucidal, a natural preservative that I introduced when I shared how to make a lotion, uses Leuconostoc kimchii, a lactic acid bacteria formed when fermenting radishes, to restrict the growth of other microorganisms.
So, in the end, I’d say that experimenting and pasteurizing a small part of your batch is probably the best idea. That way you can decide if you prefer the flavor and aroma of unpasteurized soy sauce or not. You can also judge how long your sauce tastes best, and if you think that the pasteurized sauce lasts longer or not. I haven’t had mine for long enough to give you my opinion just yet…
I’ll try to update this post as I experiment with pasteurizing part of my batch.
How do you pasteurize soy sauce?
Cook the soy sauce at 160ºF (70ºC) for at least 30 minutes.
Does Soy Sauce Expire?
It takes between 6 months and a year to even be able to make a decent soy sauce. After that, it is usually said that soy sauce will last for around 3 years as long as you have it in sealed containers. It’s not necessarily that the soy sauce will “go bad” after that, but the quality of the sauce may deteriorate with time.
Here, again, I can’t speak from experience yet, and also have read accounts from home brewers who have said that their soy sauce has improved with time. Perhaps, here, the answer is it really depends on the batch, the method used for making the soy sauce, and your expectations of what makes a good soy sauce. Soy sauce may be like a good wine that improves with time- to a point! After a certain amount of time, some wines will begin to taste like vinegar. They aren’t toxic to drink, but they aren’t pleasant anymore either.
I’ll be keeping an eye on my own soy sauce, and will let you know my thoughts in a couple of years. Meanwhile, I’d love to hear from those of you with experience making your own soy sauce. 😉
Namita Pittie
Hi Tracy,
I’ve started to make my Koji,
The mould is taking longer than you mentioned as I can’t maintain the temperature.
It’s been over a week and I’ve barely got some mould on 2 trays
They have started to smell strongly now! Do you suggest I should make moromi with whatever amount of mould I’ve got?
Tracy Ariza, DDS
Hi Namita, it’s hard to know if what you have will make a decent tasting sauce or not. All I can say is you could give it a shot to not have it all go to waste, but it’s very likely you won’t be happy with it. I’d start over and find a way to keep the temperature in the right range as it’s very important for growing the right molds. You probably have a completely different culture of molds.
Rahul Deshpande
Hi Tracy, I followed your recipe and it worked! My soy sauce is maturing in two glass bottles right now. I’ve had an issue with one of the bottles where the plastic cap blew off and the soy was exposed to air for a day or two. I’m worried it could have gotten contaminated. It smells ok though there is some scum on the top. Is it supposed to produce gas? Any thoughts on how to age the sauce safely?
Tracy Ariza, DDS
Hello Rahul!
Awesome!
That shouldn’t be an issue. Yes, it may give off a small amount of gas, especially at the beginning, through the fermentation process. I didn’t notice it because I aged it in a large jar with a lot of air space. I also opened it to check on it and stir it in those first days, which would allow the gas to escape.
I’d just suggest opening it occasionally at first to allow any released gas to escape to avoid that issue, but you’re probably past that stage anyway (?) Not sure.
I’m not sure how long it would be releasing gas at a rate that would allow for a buildup. I’d assume it’s only for a short period, but I could be wrong. (I’ve noticed similar issues with other lacto-fermentation like when curing olives. I’ll find when storing them, some of the liquid seeps out through the top of the jars!)
Rahul Deshpande
Thanks for your response, Tracy! I pasteurised the sauce from the bottle in question and there’s no buildup of gas in there. The sauce in the other bottle is still unpasteurised and building up a little gas that I vent every day. Will be fun to taste the difference. How long do you typically age your sauce?
Tracy Ariza, DDS
I just kept going until I was happy with the color and flavor. It went for over a year.
I didn’t filter it until much layer, though. I filtered out a bottle for using and left the rest.
It wasn’t until there were so many solids left that I couldn’t get much more sauce out that I finally filtered it
Rahul Deshpande
Hey Tracy, this is a long overdue follow up. Based on the info in your blog I pasteurised half of the sauce and in a few days i noticed an acidic odour in the pasteurised batch. It has progressively gotten stronger and quite unpleasant. I haven’t made up the nerve to taste it.
Now the unpasteurised batch… it is amazing! With a complex and deep flavour, my wife and I love to add it into Asian food and marinades. We gave away a lot of the miso to friends and family and they love it too.
So my experience with your recipe and process has been top notch and I’m preparing to make two new batches this coming week.
Cheers!
Tracy Ariza, DDS
Thanks so much for the update!
I’m so sorry to hear about the pasteurized batch! That’s so frustrating.
I really appreciate that you took the time to let me (us) know!
JIm
Curiosity of how Soy sauce was made brought me here.
The only question I have is how is the “mold” growing on top not the same thing that is scraped off as “mold” balled up dried and sold as the “starter fungus”?
I was thinking brewers yeast like that used in wine while first reading. I bought a whole bunch of that to make German mead but haven’t yet it’s just water, hops, brewer yeast and molasses.
It seems Asia has fermented about everything that can be fermented when looking at the recipes, whats weird is when something smells peculiar but tastes really good like fermented fish or crab sauce in green leafy wrapped rolls instead of dough wrapped for a non fried oil free option… fermented garlic is something I could eat by the spoonful it is so good I won’t ruin the flavor by saying anything about it before it is tried however if anyone hasn’t. 🙂
Thanks for sharing you experiments with various things.
Tracy Ariza, DDS
It probably is the same thing, but, of course, that’s the point. You want it to have the right strain when you grow it yourself. It’s kind of like getting a kombucha scoby and then when you ferment, you end up with another SCOBY yourself.
didi
All looks great. One comment the “green soybeans” that you mention, are not soybeans at all. They are mung beans and no relation to soy.
Tracy Ariza, DDS
Hi Didi,
They’re differences in the terminology in some countries that had made it confusing. I figured it out the hard way! 😉
Victoria
Very interesting.
Do you think it’s possible to save the mash somehow (freezing it? Drying it? Idk) to inoculate a new batch later? If this is safe/possible, I feel it would also help create more complex flavors.
Tracy Ariza, DDS
Hi Victoria,
I think it’s definitely worth a shot.
I tried drying some to see if I could use that, but so much time elapsed that I never got around to trying it.
I’d imagine it should work- it’s at least worth a shot. I’ve successfully frozen kefir grains for months and they later worked perfectly!
Kojibrother
I think if you want to achieve a beautiful dark color you should roast your wheat berries before grinding them and adding them to your moromi. It’s also very usefull for flavour 😉
Tracy Ariza, DDS
That’s a great idea that I can definitely try with my next batch! Thank you! 🙂
Andrea Hudon
Thank you so much for this blog! It is very helpful!
I have different batches of moromi that have been fermenting for 2 to 4 months. Since the beginning, I am not so confident about the way I should stir once a week (after the phase of daily stirring for the first weeks).
Should I open the jar when stirring and use a big spoon to stir or just shake/reverse the closed jar (if I do so, I guess that I should also shortly open the lid to evacuate accumulated gaz). I have the feeling that there is a risk of contamination every time I open the jar to stir.
What should I do with the neck of the jar that becomes “dirty” after stirring.
I noticed that white mold is growing on the “dirty” sides of the jar… At first, I thought it was koji, but recently, all my moromis have a strong glue smell (butyric acid?). I really think that this is due to stirring and mold/bacteria growing on the upper sides of the jar (where the moromi was in contact when stirring, but left in contact with air after stirring). Do you clean this after each stirring, and if so, what do you use to clean it?
Thanks again!
Tracy Ariza, DDS
Hi Andrea,
I didn’t really give it that much thought and did open it to stir it daily. I can see your point about contamination, but I think this also takes advantage of wild yeasts and bacteria (apart from the cultivated mold of the koji), so I’m not convinced that it’s necessarily a bad thing. Openig the jar allows you to see things better and clean the rim as needed.
Generally, with ferments, yes, you want to avoid any solids from sticking up above the liquid line or they will develop mold. (That’s why I stir daily at the beginning of making vinegar too.)
There were a few times that I cleaned the rim and everything above the liquid line with a clean cloth. I wiped everything I could away and then moistened it and cleaned it again with a clean area of the cloth. White mold isn’t likely a problem, so just try to carefully remove it as best you can, trying not to let it fall into the mixture.
Furry blue or black molds are much more likely to be problematic. White molds, especially not furry ones, are generally safe. (I studied a lot of mold pictures when making chorizo.) hahahaha
Justin
I’m currently “molding” my soy beans and wheat berries and it is going extremely well.
As a side exploration, I started looking into making my own Tofu and was wondering, can you use the Soy Pulp/Mash from making Tofu as part of making Shoyu? I really would prefer not to waste it.
I know I can make a paste similar to Miso after filtering the Shoyu.
Thank you very for an an excellent and easy to follow recipe.
Tracy Ariza, DDS
Hi Justin,
I’ve never tried it, but I don’t see why not. Maybe you could do a mixture using some fresh beans and incorporating the mash too, just in case, to see how well it works.
Alan Stevens
Hi Tracy,
I have just started your recipe for shoyu – so far all seems well.
I would also like to start a batch of Tamari, and would like to know if you have finalised your recipe.
If so, are you able to share it? If not, I plan to follow the same procedure as for shoyu, minus the wheat.
Any comments?
Thanks
Tracy Ariza, DDS
Hi Alan,
Thanks so much. I’m glad to hear it’s working well so far!
I had plans to try using the shoyu starter without wheat this summer to try a different version of tamari, but I ended up getting overwhelmed with other experiments and never got to it. I thought I’d grind up some soy into soy flour to use instead of the wheat. (I also considered grinding up some sort of non-gluten flour like tapioca starch to try instead.)
But, as I said, I still haven’t gotten around to it. When I do, I’ll probably try a few versions at once.
If you give it a try, I’d love to hear how it goes for you!
Ricky Pie
Hello I am not sure I understand it completely do you out the aspergillosis or tzar in with the soy beans and wheat and if so how much and then you said to put it in your brine and how much call me confused
Tracy Ariza, DDS
Yes, you would add the starter in step 2 under preparing the koji. Add the entire 7.5 grams.
The brine solution uses all of the ingredients listed for the brine.
“In a large glass container (around 2 gallons), mix together 1 gallon of filtered or spring water with 3.5 cups of sea salt. Stir until the salt has fully dissolved.”