Anything I’m Fermenting

May 7, 2008

Long-Winded Soy Sauce Update

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 busy!).

Kikkoman initially says: “we suggest that you use 30 g of salt per 100 ml of water used”. In other words, 30% salt (by my weird calculation) or about 23% by weight.

Then they say: “it is recommended that you use at least 15 to 16% salt, otherwise the moromi mash could decay”.

This made me panic a bit, as my salt concentration, by weight, was only 6.25%! The fermentation has been producing a fairly strong sour smell (or as my wife described it, ‘cheesy’). This is most likely from a vigorous lactic acid bacterial fermentation. As I have mentioned earlier, it was re-forming a pellicle every day (which I would break apart during stirring).

So, I drew off about 800 ml of brine and boiled it with 350 g of salt. As not all the salt was dissolving, I added probably about 200 to 250 ml of fresh water. This I then added back to the fermenting soy sauce, raising the total salinity to about 15.2% (by weight – as you may have noticed, I have stopped using my odd way of measuring salt %!).

I have definitely killed off any visible microbial action now! And it obviously tastes very salty now – in fact saltier than my Kikkoman soy sauce. On the other hand, it does not taste bad at all – it is kind of like a mix of miso and soy, with some extra acidy. Or something like that anyway.

This brings me back to my ‘back of the envelope’ calculation of the salinity of the Kikkoman soy sauce. I have to swallow my pride and say that my memory of chemistry is abominable! Here’s what I said: “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%“. Wrong. The atomic mass of sodium is 22.99 g, and chlorine’s is 35.45 g – or over 150% larger! Recalculating the salinity meant going back to the label to see that there were 920 g of sodium in 15 ml of soy sauce. This is actually 6.1% sodium, there would thus be 6.1% + (1.5 x 6.1%) salt, but wait, salt water is denser than fresh water. Again taking a short cut (this will probably end up haunting me later), I found that regular sea water (3.5% salt) is about 2.8% denser than fresh water, and dead sea water (33% salt) is about 17% denser. I just used the average – so I estimate that the soy sauce is about 10% denser than fresh water.

Getting back to the question at hand – this means that Kikkoman’s sodium % was about 5.6% (920g / (1.1 x 15000ml)), so the salt concentration must have been around 14% (5.6% + (1.54 x 5.6%)). Ah Ha! Kikkoman may have been giving Inigo some funny numbers… 14% salt is WAY less than the 23% they recommend, and perhaps even below the level at which they claim the moromi mash would decay (remember, my calculations are not exact)! Maybe they dilute their soy sauce prior to packaging? Maybe European soy sauce is much saltier than North American?

And back to my observation that my 15% soy sauce is noticeably saltier tasting than Kikkoman’s (although not so much as to be unpalatable). This is especially interesting as I use sea salt. Mark Bittman*, in “How to Cook Everything Vegetarian, states that sea salt tastes less salty than table salt. Hmmm…that means that my soy sauce’s salinity may be higher than I calculated, or Kikkoman’s lower. I think it is likelier that my soy sauce’s salinity is higher, as I have not been measure the volumes of water I have removed or added very accurately, and further, water has evaporated over the past few weeks.

Switching gears, takadi asks:

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?

I’m really not a connoisseur of soy sauces – this whole experiment has been an eye-opener. As you say, it does sound like Chinese and Japanese soy fermentation styles differ in a way like ales and lagers do. However, I cannot really say much further, as I don’t know the differences well.

The wheat is a bit of a wild card for me, in terms of its effects. I think that in traditional soy sauce making, wheat flour provides a good innoculum source for wild yeasts, lactic acid bacteria, and molds – all of which grow naturally on wheat grains. Without a reliable source of starter/innoculum/koji, farmers may have had to do with what was available. Further, wheat is likely a source of easily assimilated carbohydrates for the molds to feed on, before they are able to attack the soy beans. Unfermented soy beans are not easily digestible by humans, and it may be the same for micro-organisms. Once a culture of micro-organisms has been developed, it is likely that they are adapted to eat pure soy beans, no longer requiring the initial availability of wheat. The wheat may also make it easier to form the loaves. Finally, the wheat may survive to the fermentation stage, providing sugars for yeasts and bacteria to produce alcohol and acids, which creates ‘sanitary’ conditions inhospitable to less desirable micro-organisms. Early farmers lacked access to sanitizers or preservatives, making this last point important.

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?

Good point. Sometimes one, sometimes the other. My own brine was calculated ignoring the other ingredients, while my calculations of Kikkoman’s salinity include the other ingredients (I don’t know how much they weigh). I don’t feel like revisiting my salinity calculations right now, but I may later.

It seems as if this method relies on wild yeast strains similar to creating sourdough starter. How would effect the flavor?

Yes, this method does feel a lot like making a sourdough starter. As I mentioned in the first post, the soy patties initially smelled like my failed sourdough starter (it turned into a salt-risen bread starter). Salt-risen bread is fermented by clostridium bacteria. It makes a very cheesy tasting bread, so perhaps this has contributed to my wife’s opinion that the soy sauce fermentation smells cheesy. The cheesiness probably also comes from lactobacteria. Last weekend I tried a local brewery’s sour beer (fermented partly by lactobacteria) and it smelled cheesy. It was (personally) very over-soured – although very nice when diluted with their lager by 2/3.

“I’m also wondering how tamari is made without the addition of wheat to aid in the process of inoculating a culture.”

I really can’t say. As I say above, perhaps when a starter culture has been used for a while, it adapts to its conditions and is able to digest pure soy.

“…how do you keep the loaves warm in order for the strains to take hold?”

I kept them on top of my fridge, where it is a bit warmer. I don’t think you need to worry much about mold taking hold on your soy patties! 😉 As children discover in their school lockers and at the back of fridges, most foods get moldy sooner or later.

“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.”

I do think it would give more sun exposure, which by definition is a different environment. In fact, my grandmother just gave me a huge glass jar, and I have transfered the soy sauce into it. As the jar is much smaller than the bucket, I could bring it inside and fit in the window. Besides, you can see what is going on much better. It also seems somehow more ‘respectable’ when it is in a glass jar, rather than in a bucket!

* Bittman’s cookbooks are the only ones I use regularly. Incidentally he has a blog at the NY Times, in which he posted a link to canucklehead’s soy sauce making directions – way to go canucklehead! – around the same time I was starting to make soy sauce.



  1. Thanks for addressing my questions! You answered them quite articulately.

    I think sea salt is supposed to have more “flavor” due to the extra minerals, but I’m not sure if it is less salty. In fact, I always thought sea salt was more salty, and therefore less of it could be used to achieve the same flavor, like how they advertised on that campbell’s soup commercial. It’s either that or the saltiness is mellowed out as the mash ages.

    Also, in addition to different temperature levels, how would 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? I just thought of that sometime after I suggest putting the soy sauce in a glass jar, as the anaerobic environment might cause a different fermentation process. Perhaps the moromi mash needs to be aired out?

    It seems that 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, it could help you along with your process

    Good luck!

    Comment by takadi — May 7, 2008 @ 10:24 pm | Reply

  2. Producing a low-sodium soy sauce is definitely a fine art. It’s worth noting that Kikkoman’s low sodium version is pretty consistently rated better in taste. Of course that’s mass produced and batch processed, but a much better buy than say L’ Chepeau which is finally producing a Tamari (wheat free) soy sauce out of Dubai. Of course L’ Chepeau has always been low sodium. It’s interesting that now with the low-sodium movement for health reasons as well as the gluten-free movement, we’re starting to see better quality and varieties of soy sauce. Though of course nothing beats brewing on your own.


    Comment by El Cheapo Organic Soy Sauce — May 8, 2008 @ 6:44 am | Reply

  3. hi there,

    dont worry about the strong salt taste. it will change in time, the sweetness of the flour sugars start to be noticiable.
    i’d be concerned with the acidic taste, which shouldnt be happening

    Comment by inigoaguirre — May 8, 2008 @ 11:05 am | Reply

  4. Yea the acidic taste might be coming from lactobacilli cultures, who’s presence is there I’m assuming because of the anaerobic environment. Of course that’s an assumption, it could be the lower amount of salt he started with

    Comment by takadi — May 12, 2008 @ 2:05 am | Reply

  5. […] @ 4:30 pm Tags: Anaerobic, Lactobacillus, Making Soy Sauce At Home, Soy Sauce A couple of new issues have been brought up by Tadaki- is sea salt saltier, the same as, or less salty than regular salt? […]

    Pingback by The on-going soy sauce controversy… « Anything I’m Fermenting — May 15, 2008 @ 4:30 pm | Reply

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