Making Soy Sauce

Google reminded me this blog existed when it sent me a notice that it would be deleted if I didn't log into it. So I logged back in and was pleasantly surprised. It's fun to see what was on my mind back in 2006. 

Anyway, I just wanted a place to document my soy sauce making process, and thought this would work.

After watching a couple of YouTube videos, I went online and ordered a packet of Aspergillus sojae mold spores from a place I found in San Francisco. This was in the first week of December, 2023. The video I saw suggested Aspergillus oryzae, and it seems much more readily available, as it is used to make rice koji and sake. But it looked like sojae was for soy (the name seems right), so that's what I went with. It arrived priority delivery with a nice little note about using upcycled trash as packaging, and looked like a little baggy of green dust. I kept it in the fridge until I was ready to use it.

While I was waiting for the spores to arrive, I went to the local H-Mart in Irvine and bought a 2 pound bag of dried yellow soy beans. This is a picture I found online:

H-Mart didn't have wheat berries, so I picked up a pound at Whole Foods. 

I then soaked the soy beans in water overnight for about 16 hours. Afterwards, I boiled them for about 5 hours. 

During this time, I also roughly milled the wheat berries in a coffee grinder. They are hard, so it took a while in several batches to get them milled enough to look right. I sifted the ground wheat to separate out some finer flour. I used about 2/3 of a pound of the wheat berries total. (I wanted to lightly toast them first, but forgot.)

When the soy beans were cooked and drained and relatively cool, I put them on a baking tray lined with parchment paper and mixed in the ground wheat. I then mixed the Aspergillus with the flour and sprinkled it over the beans and wheat. I tossed them well, and spread them out evenly in the baking tray. In hindsight, I should have done the mixing in a big bowl.

I just barely warmed up the oven by turning on the flame for a second, and put a bowl of boiling water in the bottom of the oven, to create a nice warm and damp environment for the mixture to ferment for a couple of days. I covered the beans with an inverted baking pan, and let it sit in the oven.

After about a day, it looked like this (taken December 9, 2023):

Not much had changed, but the white powder seemed to be... more. Every once in a while I would just barely warm up the oven again or add more hot water. Wendy accidentally turned the oven on once, too. Over about three days, it really activated. It got nice and warm, and the spores were growing throughout the bean mixture. I would break it apart and toss it a bit to keep it from getting too hot, and toward the end I started mounding it into channels. At the end of three days, it looked like this (taken December 10, 2023.)

The mold had grown a lot, and had turned a nice yellow-green color, as it started to create spores. At this point, I made the brine. I mixed about a pound of Himalayan pink salt with a gallon of spring water until dissolved. It made a nice pink solution. I then spooned in all the bean mixture and stirred it up and the whole thing turned a rather ugly yellow-brown-green. (Taken December 10, 2023.)

I stirred it a couple of times a day. After a while, the wheat absorbed more water and sunk to the bottom in striated layers. The beans continue to float. (Taken December 19, 2023.)

It's now been about three weeks. I am stirring it once a day. I'll continue to stir daily for the first couple of months, then switch to weekly. It'll sit and age for a year. By next Christmas, I should have soy sauce to bottle. 

UPDATE: 2/10/2024

After about two months, the beans and wheat are largely starting to dissolve, and the liquid is more homogeneous without the prior striated levels. It's a yellow-brown thin sludge. 

UPDATE 5/19/24

Not much change. I'm stirring once or twice a week.  It is still a homogeneous brown sludge. It has started to grow white mold spots on top and on the sides of the jar where the sludge gets stirred up. I'll wipe down the inside of the jar and scoop out the mold when I see it. Twice I've wiped down the inside of the jar with a little vinegar and that seems to keep the mold from growing for longer. I've also tried sprinkling a little extra salt on top of the surface to up the salinity where it contacts the air. I think I just need to keep stirring a bit more frequently to keep the mold from growing. 

 

UPDATE 9/1/24

It didn't seem to be going very well. It didn't look appetizing, that is for sure. And it didn't smell like soy sauce. Not rancid or anything, just a funky feet smell. So I first replaced the glass lid with cloth to see if that would help. No real difference. On July 27, I moved it outside to try to get some sun. Several sources I read online said that soy sauce needs to be in the sun to get dark. 

Mine didn't darken at all. When sitting in the hot sun, it would separate a bit, with clear liquid patches toward the bottom. Mold continued to be an issue. But the mold was still the whiteish variety - never anything black, and I would just scoop it out. After coming back from a two-week vacation, the mold had grown into a film on top and it was easier to remove the entire film. 

After a few weeks in the sun didn't seem to be having any positive effect, I couldn't take it anymore. It looked like I had a suntea container of diarrhea on my picnic table. So on August 12 or so, I decided to strain it and put it in bottles. I first strained it through a cheesecloth lined strainer and got most of the sediment out. But the sediment was so fine, a lot got through and it was a very long process. I was not particularly patient, and so lost quite a bit of liquid. I initially had three good-sized bottles, but they were full of gunk, so I strained again and ended up with two bottles that looked like this.

The liquid was very pale, and there was still a lot of nasty greyish gunk floating on top. I let that sit outside for a few days, and still no positive changes. I thought that sediment would settle on the bottom. Nope. It just floated up on top. At this point, I took them back inside and filtered it a couple of times through a Chemex coffee filter to remove the fine sediment. I then re-bottled and put them back in the hot sun to rest. 

Filtering and bottling seemed to take care of the mold problem. Nothing has grown in there since. 

Also, after a fairly short time in the sun, the bottle with the stopper hard gotten nice and dark. The other bottle with the twist-on cap (a reused disinfected bottle that had contained ginger beer or something) had no noticeable change and was still clear and pale, like tea, or a hazy IPA. After a few weeks with the two bottles looking very different from one another, I began to suspect the reused bottle might have some sort of UV protective film or something that was preventing the sunlight from doing its thing. So I poured that one into a different stoppered bottle and put it back in the sun. Within a day it started to darken nicely.  

Now, on September 1, they are almost the same color. That's two problems down - no more mold, and it looks more and more like soy sauce. It looks like something you might enjoy. The only remaining problem is the aroma. They both still smell funky - like feet or cheese or a bit like fish sauce. I'm going to continue to let them sit in the sun and darken up for a while longer yet and hope they start to smell more appetizing. I just went to my pantry to sniff my store-bought soy sauce to compare. I have some Kikkoman lower sodium soy sauce - the kind with the green label - and it smells nice. It's kind of bright and citrusy. I also have some light Chinese soy sauce I use for fried rice, and it also smells pretty tasty. The Chinese stuff is not as fruity, and has a slightly funkier more fermented aroma. My homemade soy sauce doesn't smell like either one. A fermented funk is the only note in mine. We'll see if this turns into something anyone would want to eat. Eventually, I will boil it to sterilize it, and then filter it again to remove any last bit of sediment. I will probably taste it. We'll see.

UPDATE 10/10/2024

I threw it out. It wasn't getting better. As a last ditch effort, I brought it up to a gentle boil to pasteurize it. A bit spilled over, and when it burned on the stove, it smelled like burnt soy sauce. So I strained it again, and did a taste test. (Wendy was brave enough to try it too.) I poured a bit into a soy sauce dish, and also dished out some some low sodium Kikkoman and some light Chinese soy sauce for comparison. The homemade stuff was still a lot lighter, and it still had a distinct funky smell, but the thing is, it tasted edible. It tasted like the blue cheese version of soy sauce. It wasn't good, but it was unmistakably soy sauce. I put it back into a bottle for a few days, smelled it again, and finally poured it down the sink. 

I don't think I'm going to try it again. As much as I enjoyed the idea, I just think that the chances I could ever produce a soy sauce that tastes remotely as good as even the cheapest store bought stuff are so low that it isn't worth it. It is a bit like trying to brew my own bourbon. I might be able to make something that looks like it, but I won't be able to make anything I would consider good.