Shodoshima, the largest island in the Seto Inland Sea, is not only covered in thousands of olive trees, it also holds half of Japan’s remaining wooden soy sauce barrels. Though the island has produced olive oil for about 115 years, soy sauce has been made here for centuries — and has weathered many changes.

After World War II, soy sauce makers across Japan were encouraged to modernize their 1,000-year-old tradition by fermenting in stainless steel tanks rather than kioke (wooden barrels). But Shodoshima’s residents — like many islanders — don’t always do what they’re told by mainlanders. They decided not to use stainless steel, and today there are still 20 soy sauce makers on Shodoshima who ferment the old-fashioned way. Yamaroku Shoyu is one of them.

“In the hot and muggy summer, the shōyu moromi (soy sauce mash) becomes active, making gurgling sounds as the fermentation accelerates,” says Yasuo Yamamoto, the fifth generation head of Yamaroku. “When I walk the planks between the wooden soy sauce barrels, the moromi in each barrel becomes noticeably more active, as if it is talking to me, telling me it is happy to be in my presence. We have a mutual love for each other.”

Yamamoto speaks of his soy sauce mash as though it were a part of his family. In many ways, the moromi is the past and future of his family. Yamamoto takes this stewardship so seriously that he and two Shodoshima carpenters traveled to the last viable maker of large wooden barrels — Takeshi Ueshiba of Fujii Wood Work in Sakai, Osaka Prefecture — in 2012 to learn the craft of fashioning wooden barrels: from preparing the cedar slats and bamboo pins to weaving the bamboo hoops.

Less than 100 years ago, all Japan’s fermented products — including soy sauce, miso, mirin (sweet cooking sake), rice vinegar, sake and pickles — were made in wooden barrels. There is a good reason for this: Fermentation relies on a healthy environment where microbes can thrive, where enzymes and yeasts can work in symbiosis. Kioke are the ideal vessels for this because the wood itself is host to millions of beneficial microbes. Some maintain that the kioke is more than just a tool, it’s the essential ingredient required to authentically ferment Japanese foods.

Microorganisms thrive in Yamaroku Shoyu’s 150-year-old ōgata kioke (3,600-liter wooden barrels) on Shodoshima, creating a complex, impossible to duplicate soy sauce.

It’s worrying that kioke make up only 0.1 percent of the market today. But there is a movement afoot to preserve ancient Japanese fermentation methods before they are lost forever. Artisanal producers are banding together to support each other and to promote kioke-fermentation through education and promotion. While we will not see them disappear in our lifetimes, they certainly could in our childrens’ or grandchildrens’.

It took three days for Yamamoto and his cohorts to learn the basics of making kioke, but years of practice to get it right. They made their first barrel in September 2013, four more in January 2015, and an additional four in January of 2016. The wood used was Yoshino cedar, well-known in Japan as the best for buckets and barrels. A chance meeting between Yamamoto’s group and the head of the Yoshino Cedar Wood Products Association led to a mutually supportive relationship with Yoshino’s cedar suppliers. Since the wood needs to dry for two to three years before it can be used, the suppliers put aside boards and slabs for Yamamoto’s group.

As for the bamboo used to make braided hoops on the kioke, Yamamoto searched Kyoto for the appropriate variety but gave up due to transportation issues. He then asked a neighbor if there was any suitable bamboo on Shodoshima.

“What?” the neighbor shot back, “Your grandfather and I planted trees for the bamboo hoops years ago. Didn’t you know that?”

Yamamoto now has no more worries regarding sourcing bamboo.

According to Ueshiba of Fujii Wood Work, in the 1920s there were tens of thousands of kioke makers in Japan and by the end of World War II there were 1 million barrels left in sake breweries alone. But within a 10- to 15-year span, the number of kioke dwindled to dangerously low levels. With the abundance of metal during the postwar period, traditional wood vessels were replaced with stainless steel tanks, and many coopers were forced to close their doors. Between the ’70s and ’90s there were still master coopers in Japan, but they were aging. Ueshiba is the last master craftsman of kioke in Japan.

Today, soy sauce and miso makers who still ferment in kioke make up only a small percentage of the market, but those who continue to use wooden barrels remain convinced that fermenting the traditional way is beneficial. Sake producers, however, have not remained as committed. The National Sake Association reports that by the ’90s, barrel-fermentated sake had ceased almost completely. But from 1997 to 2000, Sarah Marie Cummings (formerly managing director of Nagano Prefecture’s Masuichi-Ichimura Sake Brewery) and the late kioke craftsman Sakuji Shimizu took up the challenge to reintroduce this traditional fermenting method. The first sake produced in a kioke built by Shimizu debuted in 2000. Thanks to the efforts of these and other passionate people, there are now more than 60 sake producers using kioke in Japan (but they still only account for 0.001 percent of the market).

“Superior products are made in these wooden vessels and there is surprisingly little research to prove what makes them so special,” says Cummings. “We hope to encourage and facilitate research and promote Japanese kioke-brewed and fermented products around the world

“With cooperation, I do believe that the kioke cooper will prosper and I am confident that there will be more great kioke makers in the future,” she says.

I have seen firsthand the excitement and pride in eyes in these few remaining producers of kioke-fermented products — people such as Yamamoto and his dedicated team of soy sauce makers. If we support them, they will flourish. The alternative would be a serious blow to the traditional food culture of not only Shodoshima but Japan itself.

For more information about Yamaroku Shoyu, visit yama-roku.net.

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