Homebrewed Soysauce (Shoyu)

Homebrew Soysauce
(Also known as shoyu in Japanese)

This is my third attempt at making shoyu, my first attempt ended up contaminated, and I didn’t have a great setup for inoculating the beans + wheat with the koji mold. The second attempt I over fermented the beans and the mold went to spore. This time I’m more prepared and I have high hopes.

A lot of people don’t know how soysauce is made and there are tons of variations depending on geographical location/ local tradition, and what was available at the time period. Here’s a quick summary of how I’m brewing shoyu:

Shoyu started 12/24/2021. I will post the final results on 1/1/2023, although I’ll likely update this post every few months.

1. Inoculate cooked soybeans and toasted + cracked wheatberries with the mold spores of aspergillus oryzae -also known as koji-. Incubate for 36-48 hours at about 85⁰F or 30⁰C. It’s important to be as sterile as possible every step of the way. I clean my kitchen before beginning these projects. I use everclear to sanitize everything, and I boil the towels I use to line my incubation chamber.

My koji chamber is a plastic tote with a reptile mat set to 85⁰F (30⁰C). On top is a perforated baking pan. I have a temperature probe in the beans to ensure the temp is maintained. There is also a small usb fan on low to allow a bit of air circulation.
In this photo I’m actually trying to make tempeh, but it’s a good view of my incubation chamber. That black wire leading to under the beans is a temperature probe.

2. After about 36 hours the beans were covered in white mycelium and my house smelled strongly of toasted wheat.

Kind of a cruddy photo, but here’s a bean magnified using a jewelers loupe.
Bean cut in half.

3. Soak the kojified beans+wheat in a 20% salt brine. I have a bit of plastic wrap on the top to keep everything submerged, and a cloth lid to top it. Stir every day for a week or two, and then stir once every week for a total of ~6 months. I’ll taste every time I stir. At this stage, the kojified beans and wheat in brine is called moromi.

Koji beans+wheat in a 20% salt brine. This photo was taken 8 days after initially submerging the koji in brine.

4. After ~6 months -if all goes well- the moromi will have become thick and it will taste salty and umami. Strain the moromi and press the solids to get every drop of liquid out of it. Age the liquid in a sealed glass bottle outside in the sun for another 6 months. Now you have homemade soysauce!

—Once I get to this stage, I will update this with a photo!—

All in all, it takes a year or more to brew soysauce so I’ll be sure to update y’all every couple of months. On 1/1/2023 I’ll be able to update you with the final results! 😱

FURTHER READING: There are tons to learn on the history of shoyu, koji mold in general, and the methods people have used to grow it over the ~10,000 years since it was discovered, etc. The methodology I’m following comes from a book called Noma’s Guide to Fermentation by René Redzepi, although I’ve tweaked a few things to fit my set up. A lot of my knowledge on koji and shoyu also comes from the book Koji Alchemy by Rich Shih and Jeremy Umanski. Instagram and twitter hashtag #kojibuildscommunity has been really helpful too. I’ve also learned a lot from Facebook groups (learning from Facebook, ironic, I know) the groups I’ve found the most helpful are The Art of Miso, and also Miso Creative: Koji off the Chain.

I sourced my spores from Gem Cultures. The reptile mat and perforated baking sheet I got from Amazon.

Gem Cultures website: http://gemcultures.com/soy_cultures.htm

Reptile mat: https://www.amazon.com/dp/B0823Q1V1P/ref=cm_sw_r_apan_glt_fabc_GHXHF4D4ZFGFMCCSNC48?_encoding=UTF8&psc=1

Baking sheet: https://www.amazon.com/dp/B00N7GMOCG/ref=cm_sw_r_apan_glt_fabc_E5FQPD9AZJ3SCSYXAY35

Usb fan: https://www.amazon.com/dp/B00G059G86/ref=cm_sw_r_apan_glt_fabc_R40V32FWRSV3NC0TAHP1

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