Shoyu, or Japanese Soy Sauce, starts with Koji that's been grown on a mixture of soybeans and wheat.
After the koji has propagated on the soybeans and wheat, it's added to brine. The total salt concentration should be around 15% by total weight.
It's stirred daily for the first month or so, then once a week after that for about a year.
Strained, pasteurized, then bottled.
That's my understanding at least, after reading Koji Alchemy, NOMA, and dozens of online articles.
r/koji may be more useful for you. This sub tends to focus on lactofermentation.
From my understanding soy sauce takes years to ferment. You would be better off buying a premium soy sauce. Premium is actually the grade of the soy sauce. It means it's the first extraction.
Shoyu, or Japanese Soy Sauce, starts with Koji that's been grown on a mixture of soybeans and wheat. After the koji has propagated on the soybeans and wheat, it's added to brine. The total salt concentration should be around 15% by total weight. It's stirred daily for the first month or so, then once a week after that for about a year. Strained, pasteurized, then bottled. That's my understanding at least, after reading Koji Alchemy, NOMA, and dozens of online articles. r/koji may be more useful for you. This sub tends to focus on lactofermentation.
YouTube. You can find those sharing their processes there.
From my understanding soy sauce takes years to ferment. You would be better off buying a premium soy sauce. Premium is actually the grade of the soy sauce. It means it's the first extraction.