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How Japan’s Fueki Syoyu Brewing Has Made Soy Sauce for Over 220 Years

This factory has been naturally fermenting the condiment the same way for two centuries

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. The soybeans are steamed and added to crushed wheat, which is important for its high amount of sugar. Mold, called Koji, is grown and put to the mix. Koji is an important part of the process because it helps break down the sugars.

The mashed soybean and wheat blend gets mixed with salt water in enormous barrel tanks. There are 38 giant barrels in the facility, with the oldest dating back to 150 years ago. There are less than 50 handmade wooden tanks for this process left in Japan, and Fueki is trying to make his own. Once in the tanks, the mash is stirred by hand with a giant dowel, which helps all the microorganisms receive air — a necessary step for fermentation and aging. This mixture is aged for two to three years, and then the liquid is squeezed out of the mash by applying 300 tons of pressure every 30 seconds. The raw liquid gets mixed and heated, and left to ferment for a week before the final step: bottling the soy sauce.

“The taste that remains on your tongue when you first put it in your mouth, and the overall balanced taste that spreads thoroughly is so rare,” says Fueki. “You can’t find the words to express the joy.”


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