Soy sauce brewing

History Terroir Craft Koji Wooden Barrel Brewing

Guided by people and water,
Kaneiwa’s soy sauce began

Kaneiwa Shoyu Honten traces its origins to the late 19th century, in the final years of the Meiji era.
In those days, when daily life was closely tied to the land, each household in the village of Ogawa made its own soy sauce and miso. Among them, the soy sauce brewed by the Iwamoto family was known for its taste. Shared among neighbors, the Iwamoto family gradually came to take on the role of producing soy sauce for the village.

Masakichi Iwamoto, the founder of Kaneiwa Shoyu, set out to refine this craft. He trained in Yuasa, Wakayama, in the Kishu region— long known as a center of soy sauce brewing— before returning to Ogawa to pursue brewing.

Drawn to the pure water known as “Kukai water,” fed by the Koyasan mountain range, he established his brewery in the land where he had always lived. In 1912, Kaneiwa’s soy sauce making began here in Ogawa.

For more than a century since, supported by the richness of the land and the clarity of its water, soy sauce continues to ferment and mature quietly in wooden barrels in our brewery.

The authentic flavors and aromas of traditional brewing have been passed down in Kishu Arida—and continue to be shared today.

Kaneiwa soy sauce,
shaped by its terroir

Ogawa, in Aridagawa, Wakayama, is surrounded by the Kii Mountains that extend from Mount Koya (Koyasan). In this land—blessed with pure underground water known as “Kukai water,” nurtured by the Koyasan range, and a warm climate where citrus fruits grow— Kaneiwa's soy sauce brewing has evolved over time.

What began within the daily lives of local farmers has grown into a craft shaped by the water, the climate, the microorganisms that live in the wooden barrels, and the hands of those who tend it— creating a flavor found nowhere else.

Kaneiwa Soy Sauce Brewing

Kaneiwa Shoyu Honten’s brewing begins by entrusting it to nature and time.

Koji, essential to soy sauce making, is first made from soybeans and wheat. It is then combined with salt water to prepare moromi (fermentation mash), which ferments and matures in wooden barrels. As it is watched over each day by the brewers, yeast and other microorganisms work quietly, developing deep flavor and aroma.

After two full cycles of the seasons, the moromi becomes a soy sauce unique to Kaneiwa.

Rigorous selection of ingredients

Whole soybeans and wheat, the foundation of our soy sauce, are carefully selected and sourced in Japan. The salt used in the brewing process is also a sun-dried sea salt, chosen with care. Because the ingredients are simple, the quality of each one matters deeply.

Ingredient preparation (soybean steaming and wheat roasting)

The soybeans are soaked in water overnight, then gently steamed under pressure. The wheat is roasted until fragrant, then coarsely crushed to prepare it for koji making. In particular, the steaming of the soybeans is a crucial step that greatly influences the depth of flavor of the final soy sauce.

Combining the soybeans and wheat with koji starter

The prepared soybeans and wheat are evenly mixed with a koji starter and placed in a warm koji room. From this point, the making of koji—the heart of soy sauce brewing—begins.

Growing the Koji

The temperature and humidity of the koji room are carefully maintained, as the koji is watched over day and night. The quality of the koji grown here greatly influences the character of the soy sauce.

Slowly Maturing in Wooden Barrels

Once the koji is ready, it is placed in wooden barrels filled with saltwater. Here, it becomes moromi—a fermented mash. Over the course of about two years, it is carefully tended and observed, as fermentation and maturation unfold. Yeasts and microorganisms living in the wooden barrels quietly go to work, developing deep flavor and aroma over time.

Pressing the Moromi

The matured moromi is wrapped in cloth using traditional methods, then slowly pressed in layers. The freshly pressed liquid is “kiage shoyu” — unpasteurised soy sauce.

Pasteurising and Bottling

In the freshly pressed soy sauce, yeast is still active. It is therefore gently pasteurised to stop fermentation and stabilise its flavor and aroma. It is then bottled one by one.

Koji —
the heart of soy sauce

Koji making lies at the heart of soy sauce brewing. Prepared in the colder months, it is carefully tended day and night, as brewers monitor temperature and humidity until the koji develops fully.

Good soy sauce begins with good koji. And good koji comes from quality ingredients and the skill of the brewer. With all five senses, the brewers read its condition and guide it with care.

The moromi made from this koji is then aged in wooden barrels for “eight seasons”—two full cycles of the year. Yeasts and other microorganisms living in the brewery, together with the forces of nature, slowly shape the deep, distinctive character of Kaneiwa’s soy sauce.

The depth of soy sauce, shaped by wooden barrels

At Kaneiwa Shoyu Honten, soy sauce is still brewed in traditional wooden barrels. Today, only a handful of breweries in Japan continue this method, making it increasingly rare.

Over many years, these barrels have come to host a living community of yeasts and other microorganisms. Their quiet activity shapes a depth of flavor and aroma that cannot be replicated elsewhere.

Time, the forces of nature, the hands of the brewers, and the environment created by the wooden barrels— together, they shape soy sauce that is uniquely Kaneiwa.

A single drop, shaped by time

Pure water, microorganisms living in the wooden barrels, and the hands of the brewers.
We will continue to offer soy sauce that slowly matures in harmony with nature.