Preserving Tradition: The Art of Crafting Authentic Soy Sauce

In Japanese cuisine, soy sauce reigns supreme as a key ingredient, yet only a mere one percent of the country's soy sauce is made using the time-honored method of barrel aging. This painstaking process can take up to four years for a single batch to transform from barrel to bottle. Meet Yasuo Yamamoto, a fifth-generation soy sauce artisan, and one of the few remaining brewers in Japan who handcrafts his own barrels. In a world where industrialization has replaced wooden barrels with steel, discover what sets authentic soy sauce apart and why the centuries-old tradition still stands strong.

At the heart of this unique craft lies the essential wooden barrel, known as "kiyoke," which can endure for over a century. Yasuo meticulously fashions bamboo strips to encircle the barrel, as the saltiness of soy sauce can corrode metal. Assembling a single barrel is a labor-intensive process, typically requiring three skilled individuals. Regrettably, this age-old practice is a dying art, with most kiyoke makers in Japan having ceased their operations.

Before these barrels are pressed into service, a mixture of crushed wheat and steamed soybeans is blended with koji, a special fungus that kickstarts the fermentation process. In a temperature-controlled environment, the fungus flourishes. After two days, the concoction finds its way to the "moromi house," where the wooden barrels create the perfect breeding ground for beneficial bacteria.

Each barrel is filled with over one ton of the soybean mixture, combined with saltwater. As Yasuo and his team gently stir the soybeans, they naturally develop tiny fissures, allowing other bacteria to enter and commence the breakdown process. To enhance the activity of aerobic yeast, air is pumped into the barrel. While Yasuo acknowledges that microbes do most of the work, his daily diligence ensures that everything proceeds as planned. By observing the scent and appearance of the soybeans, he gauges their progress. This fermentation process spans at least a year and a half, with Yasuo managing a staggering 87 barrels in various stages. His aspiration is to craft barrels that will far outlive him.

These barrels have been a part of Japanese tradition since at least the 17th century. However, everything changed during World War II when resources became scarce and expensive in Japan. Recognizing that soy sauce was an indispensable staple, the government mandated factories to streamline production, making it faster and cheaper, reducing the process from years to mere months. While larger producers modernized and expanded, small family businesses like Yasuo's struggled to keep pace. In 2003, when his father fell ill and had to retire, Yasuo stepped in, inheriting a struggling business and teaching himself many aspects of the craft.

After a year and a half of fermentation, Yasuo transfers the soybean mixture into a special machine, adding a layer of traditional wrapping cloth. Over ten days, the machine meticulously extracts the soy sauce. Although some industrial factories opt for a single pressing, Yasuo insists that achieving a high-quality product demands patience.

Following this stage, a portion of the soy sauce returns to the barrel, along with more soybeans and wheat, to undergo an additional two-year maturation process, resulting in Yasuo's signature product, Saishikomi – a richer, more robust soy sauce. The extended fermentation period allows the soy sauce to develop a delightful sweetness in its aftertaste, a characteristic that chefs like Hitoshi Kishimoto highly value.

Hitoshi, who has been running his restaurant, Koyomi, in Shorashima for five years, relies on naturally fermented soy sauce for nearly every dish. He insists on using Yasuo's brand, as its authentic flavor enhances his culinary creations. To ensure the tradition of barrel-aged soy sauce endures, Yasuo conducts barrel-making workshops each year. His authentic soy sauce finds its way to customers worldwide, priced at $35 per bottle on Amazon, roughly triple the cost of commercial alternatives. For Yasuo, passing down the legacy of barrel-aged soy sauce is not just a mission; it's his life's work.