Homemade Soy Sauce Experiment Instructions

What is the craziest experiment you ever did in your kitchen?
What is the most complex and complicated kitchen experiment you ever did?
What is the grossest, most disgusting sounding food you ever made?
What foods, when you make them, do you really not want to share how it is made with the people eating them?

In response to all those questions above, I have one answer.
Homemade soy sauce.

I'll warn you now, this blog post is not for the faint at heart or the squeamish. It may easily gross you out completely, and one thing it'll certainly do is change your view of a commonly eaten condiment.

So, if you'd like to take the blue pill, do not read on.
But if you take the red pill and find out the freaky truth about the origins of your food, you won't ever be able to forget it. You'll never be able to look at a bottle of soy sauce the same way again.

The choice is yours.

Blue pill?

Or red pill?

If you want to take the red pill, read on.
How Soy Sauce is Made
Soy sauce is probably the condiment I use the most in my house. I use it with starches. I use it with meats. I use it with beans. I use it with vegetables. I use it with fish. I use it in soups. I use it so much that I've wanted to make it on my own, because when purchasing a bottle of soy sauce, I have two options.
Buy a small, expensive bottle made from all sorts of chemicals, from food coloring to artificial flavorings, etc...
Buy a large, pretty expensive bottle of soy sauce made the traditional way, with only 4 ingredients. Soy, wheat, water, and salt.

I chose option number two, because I value my health more than my pocketbook, and with the frequency that I use soy sauce, I wanted as natural as possible.

That was, until I started on my gluten free diet.
Even when I first went off gluten, I was able to have soy sauce without a problem, but I've become so sensitive to gluten that even the small amount of wheat in the soy sauce when used as a condiment is enough to make me feel sick for hours, so gluten free soy sauce it is.

Only the gluten free soy sauce available where I live is pretty nasty stuff. So full of chemicals, not to mention dreadfully expensive.
But I have a really hard time living without my soy sauce, so I've been using it, high price, unhealthy, and all.

But if I could make my own gluten free soy sauce, make it cheaply, and ensure that there were only natural ingredients in it, then I would be thrilled.

And so, I started researching how soy sauce is traditionally made.
I found out something quite disturbing.
Not disturbing in a moral sense, but disturbing in a "churns my stomach" sense, because it was so gross to think about. I can't look at a bottle of soy sauce the same way now.

The traditional process of making soy sauce involves the following steps:

Cooking soy beans until soft.

Mashing them, mixing them with wheat flour, and making them into cakes.

Putting the cakes in a warm, moist place for a week or two to allow mold to grow all over the soy cakes. (Yes, MOLD. I'll get back to that in a little bit.)

Put the cakes into the sun to dry out completely.

Put the cakes in a very salty brine in a container in the sun.

Let the soy cakes ferment in the sun for a long time.

Strain out the liquid. This is your soy sauce. The solids left behind is miso.

That's it.

Make soy cakes, let them mold, then ferment them in salt water. Sounds absolutely delicious.
Sounds disgusting.

MOLD?!?!?!?!? Doesn't that kill you?!?!?!

But you know what? Even though we think of molds as completely disgusting and dangerous, there are quite a few molds traditionally used in food preparation.

Blue cheese, for example.



And of course, soy sauce.

Mold is just another type of fungus. A cousin of baking yeast and shitake mushrooms.

Some molds are dangerous to eat. Some are safe.

But with soy sauce, you don't eat the mold. You kill it by placing it in such a salty brine that the dangerous microbes in the mold die, leaving only the salt and heat resistant non dangerous microbes, which then, as you let it ferment in the heat of the sun for at least a month, preferably more, turn the brine and the soy cakes into what we know as soy sauce.
And then if you want, just to be on the safe side, you pasteurize it.

So there's absolutely no danger from the mold.

It just takes some getting used to.

Soy sauce, if not made from chemicals, is just fermented moldy salty soy bean cakes.

And that is perfectly all right.

People have been making and using soy sauce in their homes for thousands of years. It is totally safe to do. It just takes a mindset adjustment and a rock solid stomach, not to mention the ability to keep your mouth shut when serving foods made with your soy sauce to guests.

After my research on soy sauce making, I decided to experiment with making gluten free soy sauce. Instead of using wheat flour, I made the soy cakes from soy beans and rice flour, and then continued the rest of the process the normal way. I also made a few soy cakes with wheat flour, which I'll be fermenting separately, as a control for my experiment.

I know that homemade soy sauce with wheat flour will definitely work, as I've seen many people on various cooking boards made it and it ended up great, but since I haven't seen any such things written about people's experience making soy sauce with rice flour, I'm certainly doing an experiment. I have no guarantee that it'll work, but I figure its worth a shot anyhow.
I don't see why it shouldn't work, as wheat is just the binder, not the main ingredient, and it is possible to make soy sauce with other grains aside for wheat, at least according to Wikipedia.

But we shall see.

I have no results yet from my experiment, but wanted to share what I've done so far, so that if anyone else wants to experiment alongside me, they can get started while it is still summer, and don't need to wait until next spring to get started.

Making Homemade Soy Sauce- Instructions

1. Buy organic, non GMO soy beans, and cook them in water until they are really soft. This may take quite a few hours.

2. Mash or blend your soy beans to get as smooth of a paste as possible. This won't be easy, because even once soybeans are soft, they still don't mush like other beans do. If you still have chunks, that is completely ok. You just want it mashed enough that you can form it into cakes.

3. Mix the mashed soy beans with flour, either wheat flour or rice flour, so you get a semi workable dough. If you need to, add some water to help it hold together more. Add as much flour as you need, no specific ratio is needed.

4. Put the soy bean cakes in a warm, moist place until it starts growing mold. I put mine on a cookie tray, lined with parchment paper, covered it with a damp towel, and placed it in a less frequently used area in my non air conditioned house.
The towel dried very quickly in the heat, so twice a day I poured more water onto the towel so that the soy cakes were able to remain sufficiently moist.
After about 1 week, the soy cakes were covered in a nice large layer of mold. Many different types of mold. Some black, some grey, some green, some white. Some fuzzy like cotton balls, some barely noticeable. It doesn't matter. A mixture is fine.
(Suggestion- do not copy my idea to put it on parchment paper. It sticks to the parchment paper and is very hard to remove. Next time I think I'll use silicon baking paper.)

5. After the cakes get sufficiently moldy, put them in the sun for a few days until they are completely dried out.

6. Make an approximately 25% brine. What that means is, for every 2 liters (2000 milliliters or grams) of water, add 500 grams of salt. That's approximately 2 quarts of water and one pound of salt.

7. Put the moldy soy cakes in the brine in a non metal, food grade container. I couldn't find exact proportions of soy cakes to brine, but I read that you should put the soy cakes in, and make sure it is covered all the way with brine, then add a drop more. You can roughly see the proportions I used in the pic below.

8. Cover your container with a wire mesh, so that the sun will still shine on your brew, but no dirt or bugs will fall in. I used some old screen, left over from our homemade dehydrator.

Gluten free soy sauce to be.

Soon to be soy sauce with gluten. The control for the experiment.
9. Leave in the strong summer sun for at least 1 month, preferably more. Mix it every two or three days. The longer it ages, the better it tastes. 4-6 months is recommended to allow it to age, but I plan on reporting back to you readers after a month how it tastes.

Note: Water WILL evaporate. Add boiled water to the mixture to replace what is missing. Make sure that the brew doesn't get rained into.

At the end of the brewing process, the liquid in the container is soy sauce; the solids are miso. Strain out the liquid, and if desired, pasteurize on the stove top.

I'll update you with another post, and my opinion about the end result, when I do that.

But isn't soy unhealthy?
Soy has a few different issues.
One of them is the fact that nearly all soybeans sold in the US are genetically modified, which is controversial healthwise. I don't know enough about the subject to make definitive statements on the matter, but I know there are claims that GMOs can be carcinogenic, and that because they're genetically modified to be resistant to pesticides that would kill everything else, they tend to be much more heavily sprayed than even regular non organic.

Soy also contains phytoestrogens, something that when ingested, is treated by the body as something like estrogen. The jury is still out on whether this extra "estrogen" is beneficial or harmful, but I've read that it may cause boys to grow breasts, may increase the likelihood of different women related cancers, among other things.

Because I use organic, non GMO soy beans for making soy sauce, the GMO isn't an issue.

The long fermentation process that soy sauce goes through destroys the phytoestrogen in the soy, eliminating the possible issues caused by phytoestrogen.

The only issue, as far as I see, remaining, is that all naturally brewed soy sauce ends up with a naturally found type of MSG, free glutamates specifically. I personally have no issue with that, as it is naturally found (and is also found in broth made only from animal bones, no soup mix) and naturally occurring. I react badly to artificial MSG, but natural glutamates don't have the same effect on me.

Other than that, there is just the possible issue of ingesting too much sodium. But as no one drinks soy sauce plain (I hope), its no different than using salt to flavor your food, and I wouldn't be concerned about the salt intake.

So, how frequently do you use soy sauce, or any thing derived from soy sauce (including worcesterchire sauce and terriyaki sauce)? What type of soy sauce do you usually use? Naturally brewed or with chemicals/additives?
Are you a little shocked to learn how soy sauce is made? Does it make you view soy sauce differently, or not at all?
Do you think you'd ever try to make your own soy sauce at home, or is this long and drawn out, mold involving experiment, a little too much for you?
If I served you some of this soy sauce if you came to my house, would it freak you out?
Do you think my experiment will work?

Linking up to Real Food Wednesday, Tuesdays at the Table, Traditional Tuesday, Works For Me Wednesday, What's Cooking Wednesday, Homestead Barn Hop, Healthy 2day Wednesday, Women Living Well Wednesday, Mangia Monday, Full Plate Thursday, Pennywise Platter Thursday, Turning the Table Thursday, Fight Back Friday, Foodie Friday, Food on Friday, Wellness Weekend, My Meatless Monday. Hearth and Soul Blog Hop

Penniless Parenting

Mommy, wife, writer, baker, chef, crafter, sewer, teacher, babysitter, cleaning lady, penny pincher, frugal gal


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  1. I am curious how your soy sauce (with rice) turned out. Any photo? Feedback on taste, please.

  2. Me too. :-) Any update?

  3. How did it taste? Yikes. Enlighten us!

  4. Yes, very curious to know how your soy brine turned out! Uh oh, Penny, did you survive the experiment? are you still with us?

  5. This is a great idea! I would start with a mold culture, so you know that you're using something safe for human consumption. Try a search for "culture for miso." (Not all molds are okay to eat. The mold itself isn't the only concern. Some molds make toxins, and some of them are extremely nasty, like carcinogenic aflatoxin. If you start with a culture, you minimize the risk of growing anything undesirable.)

    1. To anonymous, the mold comes from the air. Air borne mold and bacteria is what allows things to ferment or mold over, you don't "add" a mold, it occurs naturally.

    2. to mj, you don't have a clue what you're talking about. adding bacteria is the difference between a good fermented product and a half-assed one.

    3. to mj, sure you can add specific mold, yeast, or bacteria to production of food. That' s how people control the quality of their production of cheeses, wine, soy sauce, beer, or even bread. All of the three said microbes can be found in the air. Human extract them, culture them and use them on right products.

    4. So Anonymous, you're calling everyone who makes fermented products without starters half-assed?? I would just like you to know that the list includes all your ancestors and mine, so you basically just dissed everybody from dead people to bakers and brewers.

    5. So... The addition of cultures is only nessisary if you are not following a traditional method. The tradition of brewing soy sauce is very safe, in fact most fermented foods are more complex in flavor when made without isolated cultures because each individual species involved gives its own flavor. I hope nobody gets sick from trying it too soon. The reason it is safe is actually because of the lactofermention of toxins produced by the mold. Also the mold doesn't come from the air, it is actually from the raw wheat flour. The microbiology of a rice paddy would likely be quite different from that of a wheat field. I am interested in how this turned out.

    6. yes, using whatever yeasts and molds happen to be floating by is half-assed. i don't know about your ancestors by mine were cultivating yeasts and molds for a long time. mothers for sourdough, specific yeasts for brewing and distilling, and particular molds for different types of cheeses. i would not serve soy sauce made with wild molds/yeasts.

  6. Aloha from Hawaii! I too would like to make my own soy sauce and gluten free soy sauce. You seem to be the only one I could find who has done or is doing soy sauce with rice flour. It seems that from the time of your post that your experiment should be ready. Is it? Please share or I am afraid I'll have to start reinventing the wheel :) Mahalo.

  7. We all would love to hear the results of your experiment. :)

  8. What happened with your homemade soy sauce experiment?

  9. The whole of your process is right but the molding paste. You should use the mold named Aspergillus Oryzae, otherwise you can not control which molds is growing in the paste. As you knew, some kinds of mold are useful, some are dangerous for health.

  10. This is an interesting read on Aspergillus oryzae, just as an FYI.

  11. I wanted to Address a Couple of things i Noticed with this. First off as the Original Soy Sauce Comes from China Rice or Rice Flour was Probably used in the Original Recipe The Second thing i want to Address was the Comment on Useing Cultures to Start this is a Modern Tecnique but not a New thing entirely People have used a bit of Sour Cream to Start New batches, Sourdough Bread is Made from a Starter or a mother, Cheese is very Common Food Started from Cultures, Cultures are the Same as the natural Bacteria or molds they are just grown or "Cultured" to make Control of harmful Growth easier. hope this helps clear up some of the misunderstanding i seen in the Comments and To the Original Writer of this Thanks i Looked for a Recipe to make it and all i was finding was Recipes that added to the finished Product.

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