Anything I’m Fermenting

April 22, 2008

Soy Sauce Part 3: Brining

Filed under: Soy Sauce — iwouldntlivethere @ 3:36 pm
Tags: , , ,

Step 9: Make brine solution. I ended up using a solution of 3 liters (or 3000 g) of water with 200 grams of salt. This is a 6.7% salt solution*.

Step 10: Ferment soy chunks in brine for a few weeks. My fermentation took place in a food-grade plastic bucket, covered loosely by cling wrap held in place with an elastic. It is placed in a large west-facing window in a room that heats up considerably in the afternoon**. I try to stir it once a day. I have noticed that the soy chunks stayed whole for a few days, before breaking down, although a few are still fairly whole. Initially the fermentation produced some bubbles, but that stopped after the first few days.

The fermentation does not have a strong smell as it is partially covered. Even when open, during the first week it had only a mild, fungal smell like freshly cut button mushrooms. After about a week the fermentation formed a pellicle – a bacterial/fungal mat covering the surface (see photos). As well, when the cling wrap covering is removed a somewhat stronger smell is apparent. However, the smell is not unpleasant, being quite yeasty, somewhat like beer fermentation, but more earthy (and obviously without hop aroma). Directly smelling the spoon used to stir the brine brings out again the fungal smells, but also a sour smell – probably lactic acid bacteria. Haven’t had the courage to taste it yet though!

* In this case ‘canucklehead‘ was a bit vague about the amount and strength of the brine. At first he suggests: “the fermented disks are soaked in a brine that contains 8 oz of salt” and later “start out with 4lbs of water with 4 oz of salt”. That works out to about a 6% salt solution, by weight. I checked the label of my ‘naturally brewed’ Kikkoman soy sauce, and the salt concentration is about 7% by weight. So that seemed to be a pretty close match.

I also came across (have lost the link) a Google book about food safety in food processing . They talk about brining and different strengths and uses of brining. They said the minimum safe concentration of salt is about 10%; however later when discussing fermentation (of sauerkraut or pickles) they suggest concentrations of around 8% in order to allow the lactobacillus to thrive. This makes sense, as above 10% the fermenting organisms themselves are inhibited.

Canucklehead’s 4 lbs of water is about 2 liters, so I may be making a more dilute soy sauce (i.e. more brine per soy), but he says initially that his brine contains 8 oz of salt, which means that he would have needed about 4 liters of water. In that case, my soy sauce would be more concentrated. As with brine strength, I have gone with a middle estimate.

Subsequently on the eGullet forum on which canucklehead has been posting, “inigoaguirre” posted a link to his blog (unfortunately for me, in Spanish) showing some pictures of his soy experiment. As well, he states that:

the brine should have around 25% salt (you should heat at least a part of the water in order to dissolve the salt otherwise you would end up with all the crystals in the bottom). Kikkoman uses for their classic soyzu 23% salt; you can also find soy sauce with low salt content, but the proportion should still be quite high”

Not sure about this – on one hand, it looks like his soy sauce fermentation has succeeded (see his blog). Salt concentrations of 25% or so would definitely need boiling water to create the solution. However this concentration is well above canucklehead’s suggestion, and does not correspond to what my Kikkoman soy sauce (not low-sodium) bottle’s label states (you can calculate it yourself: per 15 mL serving there is 920 g sodium). What’s going on?

One idea is that Inigo and I are calculating salt concentrations differently (I’m fairly seat-of-my-pants on this). Although his statement about heating the water suggests that his salt concentration is indeed higher than mine (which just required a bit of stirring to dissolve). Also, the Kikkoman label deals with sodium, not salt…so the chloride part of salt is not included. As I am too lazy to revisit my high-school chemistry on molar weights, I have not bothered to figure out how much this affects my salt concentration calculations. My guess is not enough to bring my figure up to 25% though – chlorine is much smaller than sodium, and even if they were the same size, it would double the salt concentration to around 14%, still far from 25%.

Another hypothesis is that Inigo’s fermentation may not be via active bacterial/yeast culture. Rather, leftover enzymes (from the molds on the soy patties) that are not denatured in the saline environment may be causing the soy sauce to ferment. As well, if these enzymes produce acids, or if the mold produced acids in the soy patties, and Inigo has placed his fermentation jar out in the hot Spanish sun, he may be creating low-level acid hydrolysis reactions. Acid hydrolysis is how a lot of cheap ‘soy sauce’ is produced – although under industrial conditions using heavy duty acids and high heat and pressure. This is pure conjecture!!!

** Canucklehead says:

Large containers sitting out in the sun (under plexiglass). I actually don’t understand why this needs to be done – but my uncle says that my grandmother would always let the sun cook out the water – sometimes for a whole month. Perhaps this was a way to remove impurities – when tap water was not so safe”

I don’t really agree with his theory – based on what I have read about the manufacture of soy sauce, it is more likely that this practice was to warm up the fermentation, speeding it up, and creating more intense flavours. In Japan, before WW2, soy sauce was usually brewed during spring or fall specifically to achieve a mellower flavour from cool temperature fermentation. This also corresponds to beer brewing – fermenting at higher temperatures creates a lot of extra flavours that are not usually desirable in beer.

As this soy sauce recipe appears to be of Chinese origin, I have put my fermentation bucket in a warm spot in a very sunny west facing window.

Canucklehead goes on to discuss something I have read fairly frequently elsewhere on soy sauce fermentation:

I mentioned that they looked awfully pale to make a dark soy sauce – but he said that the brew will darken as it sits in the sun. “Just like how people get tanned.” Huh? I don’t understand how it can get darker – the brine is very salty – so I assumed that there would be no further fungal growth – but how can it get darker?”

Based on what I have read of Japanese soy sauce manufacture they ferment and age their soy sauce in the dark, and their soy sauce turns quite dark without exposure to the sun. The soy sauce is made dark likely by using roasted wheat, by pigments from the molds, by reactions during fermentation, and perhaps due to oxidation (like how an apple’s flesh turns brown with exposure to the air). On the other hand, it really may be that the microorganisms ‘get tanned’ somewhat to protect themselves from UV radiation by producing some sort of pigments.

And just to clarify (“I assumed that there would be no further fungal growth“), there is definitely active growth by microorganisms in the brine – from what I have read this includes most of the organisms involved in brewing beer: yeasts (kloeckera, saccharomyces, brettanomyces and probably others), and bacteria (enterobacteria, pediococcus, lactobacillus, maybe the clostridium and probably others). I doubt the molds themselves are able to grow so canucklehead is partly right – they are likely inhibited by the anaerobic and saline environment of the brine. So I believe their primary purpose is to pre-digest the soy beans and provide extra enzymes for the fermentation. They are themselves probably consumed by the fermentation yeasts and bacteria.


  1. hi,

    from what i have been researching, salt concentration should at least be 20%, and you might be able to go down to 18, but not lower.
    the reason behind it is that if you don’t have enough salt concentration you would not kill the mold and it would still be in action.

    the purpose of the salt brine is to kill the mold and maintain the enzimes alive and fermenting.

    i have never heard that this is applied to cheap soy sauce, but to traditional soy sauce.

    re. the pellicle that has appeared, i think you should remove it (this is what recomends in the book of miso)
    check this “recepie” on the book of miso on google books (making traditional japanese shoyzu):,M1

    Comment by inigoaguirre — April 23, 2008 @ 11:56 am | Reply

  2. Hi Inigo,
    Thanks for the link to that google book on miso and shoyu making! It’s a very good resource for me.
    Based on its recipe for shoyu here are my calculations for salt concentration. One assumption I had to make was that the weight of the cooked beans was 2.5 times larger than the dry beans. This is roughly what I have experienced cooking beans to a crumbly consistency. The other assumption is that the wheat was not cooked (as the recipe did not say so).
    Please note that rightly or wrongly the way I have been calculating salt % is the ratio of salt to the other ingredients (NOT the ratio of salt to the combined weight of all ingredients INCLUDING salt) i.e. if there was 1 part salt to 3 parts everything else, the % would be 33%, not 25%.

    Wet Beans: 25 lb = 11350 g
    Dry Wheat: 10 lb = 4540 g
    Salt: 8 lb = 3632 g
    Water: 28 lb = 12712 g
    total (excluding salt): 28602 g
    % Salt: 12.7%

    So, this recipe places the salt concentration at around 12.5%, by my way of calculation. If your method of calculation means that this is 25%, then perhaps you could say that my soy brine’s strength is around 13%. Another thought occurred to me – that perhaps your salt concentrations % are in salometer degrees (see If the salometer reading is 25, that is about 6.5% salt by weight (or about 6.9% by my method of calculating).
    The more I read on salt concentrations, the more the salt concentration recommendations vary! On one level, it does seem that my salt concentration is at the lowest end considered safe. On the other end are recommendations for 18% salt for shoyu fermentation. What may be happening is that shoyu fermentation, taking place over a year or more, can handle 18% salt, while the Chinese recipe that canucklehead provides is based on much faster fermentation, so requires lower salt levels. As well, if the shoyu recipe calls for adding wet soy patties to the brine (as opposed to the dry ones I used based on canucklehead’s recipe), then a lot of water is contributed from them, reducing the ultimate brine strength to around 13% as I calculate.
    I do understand that the point of brining is to inhibit the growth of undesirable bacteria and molds. However, I’m also sure that it is not meant to be high enough to inhibit all microorganisms – so it should maintain some microorganisms, as well as any remaining enzymes from the molds.
    What I meant by the acid hydrolysis hypothesis is that if you and I are really measuring salt concentration similarly, then your salt concentration of 25% is high enough to stop ALL microbial growth and fermentation. In that case, the fermentation that has occurred must be due to some other factors – and I suggest that it may be a result of continuing enzymatic action (even though there are no living microbes), and/or due to a form of natural acid hydrolysis due to the presence of amino acids and salts in a warm, acidic environment.
    I think the pellicle is rather cool! Even if I tried removing it, it would likely keep coming back until this phase of fermentation has completed, so I just stir it in during my daily stir. If this is anything like beer making, as the fermentation digests all the simple sugars and proteins, it will proceed to the longer chain sugars, starches and proteins, and thus change what types of microbes are at work, and the pellicle may disappear. This morning the pellicle had re-formed.

    Comment by iwouldntlivethere — April 23, 2008 @ 4:55 pm | Reply

  3. hi again. the only way i calculated salt ratio is in relation to the water, without having into account the solid matters.
    what i did was much simpler, i put all the dried chuncks on the bucket and added the brine till it covered all the pieces.

    Comment by inigoaguirre — April 28, 2008 @ 7:09 pm | Reply

  4. Hi there, I hope you continue documenting the progress of your soy sauce. I’ve been following inigo’s, canucklehead’s, and your processes.

    I think it’s interesting you mention the differences between chinese soy and japanese soy and compare it almost to the differences between an ale and a lager. Perhaps that’s why Chinese soy sauces tend to be more robust and Japanese soy sauces more delicate. Would the ratio of wheat have anything to do with the fermentation process either?

    When you talk about percentages of salt, do you mean percentage of salt in the brine, or percentage of salt total including all the other ingredients?

    I read inigo’s post on egullet mentioning how there are different strains of koji used in shoyu making as well. There’s brown rice koji, shiro koji, aspergillus oryzae, aspergillus sojae, etc. It seems as if this method relies on wild yeast strains similar to creating sourdough starter. How would effect the flavor? I’m also wondering how tamari is made without the addition of wheat to aid in the process of inoculating a culture.

    Also, besides draping the loaves in damp towels and newspapers, how do you keep the loaves warm in order for the strains to take hold?

    Anyways, I think I’m going to start my own batch in a couple of weeks. Do you think keeping the mixture inside an open glass jar would be a different environment than keeping it in a plastic tub? There would definitely be more sun exposure.

    Comment by takadi — May 2, 2008 @ 5:47 pm | Reply

  5. Also, in addition to different temperature levels, how will the level of oxygen exposure, especially during the fermentation of the moromi, affect the final product? Is it recommended that the container full of the fermenting mash be kept in an anaerobic environment, and aerobic environment, or something in between?

    As you stated, there are alot of similarities of soy sauce production to brewing beer, so perhaps inspiration can be found there.

    I found a great site which lists the processes of soy sauce production patent

    Comment by takadi — May 2, 2008 @ 6:58 pm | Reply

  6. Also, in addition to different temperature levels, how will the level of oxygen exposure, especially during the fermentation of the moromi, affect the final product? Is it recom mended that the container full of the fermenting mash be kept in an anaerobic environment, and aerobic environment, or something in between?

    As you stated, there are alot of similarities of soy sauce production to brewing beer, so perhaps inspiration can be found there.

    I found a great site which lists the processes of soy sauce production patent

    Comment by takadii — May 2, 2008 @ 7:00 pm | Reply

  7. […] Sauce I’ve been digesting what Kikkoman said to Inigo for a few days now, as well as what Takadi has asked (sorry about not responding earlier…it has been […]

    Pingback by Long-Winded Soy Sauce Update « Anything I’m Fermenting — May 7, 2008 @ 3:30 am | Reply

  8. 920 mg in 15 mL serving is = 15.6% concentration by weight.

    920mg of sodium = 58.5 / 23 * 920 mg of sodium chloride (NaCl)
    = 2.34 g of sodium chloride.

    2.34 g in 15 mL = 1000 / 15 * 2.34 g of salt in 1000 mL of water
    = 156 g of salt in 1000 mL
    = 15.6 % concentration by weight.

    Comment by Morning Dew — October 8, 2009 @ 4:37 pm | Reply

  9. Greetings! Your blog is so very inspirational! Thank you so much for sharing your experience making this artisanal, homemade product. As I prepare to make my first batch of miso, I am moved to contact you with a question and introduce myself.

    The art of zymurgy (fermenting things!) is a passion for which I had no idea to which I would take such an immense liking. for me, it all sprang from a desire to preserve my garden’s harvest through methods which don’t sterilize and render them less nutritive. The subsequent discovery of lacto-fermenting foods (etc.) has changed my life irrevocably.

    Through my pursuit to learn about the safety of preserving food without canning, I discovered a textbook on the economic microbiology of fermented foods. within this book is a chapter on miso & soy sauce. After learning that making miso & soy sauce is not complicated, I have become infected with the desire to try it. When I went to my local Asian market,they did have the culture. It is by a company called “Cold Mountain”, and it is the Aspergillus Oryzae culture in rice. Their directions say to inoculate soy beans with the (rice & culture) contents. It is optional to add a tablespoon of already prepared (live) miso. What I wonder is how I will make the second batch; will I have to keep buying the spore, or can I use some of my last batch instead of buying the culture fresh each time?

    Comment by Julie — November 25, 2010 @ 5:40 am | Reply

    • Glad to hear this blog is useful! I don’t really have the time to update it, but such is life. Anyways, in response to your question, I’d say that unless you do something during the process of making your miso that would kill the culture like boiling it or heavily salting it, you can reuse the culture.
      For homebrewing I keep yeast strains going, instead of always buying more yeast. What I do is carefully sterilize by boiling some baby-food jars, and after sanitizing everything (scissors, package, my hands, etc) with a no-rinse sanitizer (like Star San, Iodophor, etc.) I split the culture I buy between the jars. When I want to use some of these cultures, I make a yeast starter with sterilized wort and add one of the jars. I re-use this yeast a couple times, then start with another baby-food jar.
      I think you could adapt this process to miso culture by pressure-cooking some brown rice with water in jars (thus cooking and sterilizing it and the jar), then carefully innoculate the jars with the miso culture you buy. Keep in the fridge.
      Good luck!

      Comment by iwouldntlivethere — November 25, 2010 @ 4:08 pm | Reply

  10. […] I wonder how DIY sodium content will be?  I found these calculations over at Anything I’m Fermenting: […]

    Pingback by His and Her Stir Fry: Low Sodium vs Gluten Free | Brain and Head Health — May 27, 2011 @ 4:06 am | Reply

  11. I just want to say, I’m enjoying the discussions about making your own soy sauce so much through the various threads.

    I’ve made my own rice wine (hwang jiu) and plan to make my own tempeh.

    I live in the tropics so I’m really looking forward to lots of mold and fermentation.

    Comment by Lam Dao — October 20, 2015 @ 4:01 am | Reply

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