At Japan’s Fueki Syoyu Brewing factory, Masatsugu Fueki uses the same natural practice of making soy sauce that his predecessors used over 220 years ago.

“We’ve been following these rules from a very long time ago,” he says. “I am trying my best to keep tradition every day.”

Though the finished product only consists of three ingredients — soybeans, wheat, and salt — the presence of microorganisms complicates the delicate process. Fueki uses protein-rich Oosuzu soybeans from the Aomori prefecture.