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Reproducing Shogun-Era Shoyu in Kozaki Fermentation Town

Although the shoyu-making process has remained almost unchanged since the Edo period, the manufacturing method is quite different. How exactly was shoyu manufactured hundreds of years ago? How different is it? Hanji of Fujihan Shoyu said, “Both aroma and taste will be very different if the shoyu were handmade. We don’t use machines to make a lot of shoyu koji at one time; instead, we meticulously warm it up in our koji malt chamber with coal briquettes.”

When you enter the Fujihan brewhouse, a chilly air flows around you. A dark brown open-timbered roof has been supporting this building for 140 years. Six huge wooden barrels, which were used more than 100 years ago, are located next to the newly-built koji malt chamber. The inside of the chamber is a space of about 15 square meters. There is an internal door which opens to reveal another space behind it. This is where shoyu koji, the original form of shoyu, will be made.

In the Edo-period method, soybeans are boiled for hours and mixed with ground roasted wheat. After the home-made koji is blended, it’s fermented in the chamber. Fujihan uses only organic soybeans and wheat made in Chiba in this reproduction attempt. The soybeans must be used whole. When mass produced, processed defatted soybeans are used to quicken fermentation. Defatted beans take six months to make shoyu, but natural whole soybeans take at 12 or 18 months to ferment. Depending on the weather, it could take two years.

Unlike mass production, which in many cases uses rotary roasting kilns, the wheat is roasted by a flat kiln. When a flat kiln is used, the wheat crisps and produces a fragrant aroma. Umami is also increased, since heating using a flat kiln inflates the wheat. By so doing, the starch level increases. Both aroma and taste become richer.

Another difference is shoyu koji. In the mass production method, koji is made by machine. In the Edo period, such machines didn’t exist. They used to use wooden boxes called kojibuta to make koji in smaller portions. The reason for using these boxes was to control the temperature of koji. Koji generates heat when gathered, and the heat has to be dispersed to sustain optimal conditions. Using these boxes prevents the koji from heating up rapidly. By layering the boxes, heat is released through the gaps between the boxes, and the temperature can be controlled. This is wildly inefficient; it requires more hands.

“Of course it takes more time and labor, but by applying the older method I can show how to make shoyu more descriptively. In a big factory, you can’t tell what’s being done visually,” Hanji says. “I hope people are excited to witness how to make shoyu and feel familiarized with it, at a time when it’s not as popular as it used to be.”


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