The 1,500-Year Journey of Japan’s Rare Shiokara Natto

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Not Every Natto Is Sticky

For many people outside Japan, the word natto brings only one image to mind: sticky fermented soybeans served over hot rice.

That image is understandable—but incomplete.

Long before sticky natto became a familiar breakfast food, Japan already had another soybean fermentation tradition.

It was darker.

Saltier.

More concentrated in flavor.

And today, it is produced by only a handful of traditional makers.

This food is called Hamanatto.

Unlike ordinary natto, Hamanatto is not fermented with Bacillus subtilis, the bacterium responsible for sticky natto.

Instead, it follows an entirely different fermentation method that begins with koji mold (Aspergillus oryzae), followed by salt maturation and drying.

The result is not a side dish but a powerful seasoning ingredient with an exceptionally rich umami profile.

Although it shares the word natto, Hamanatto belongs to a completely different culinary tradition.

Understanding that distinction is the first step toward understanding one of Japan’s most remarkable fermented foods.

What Is Shiokara Natto?

According to Japan’s Ministry of Agriculture, Forestry and Fisheries (MAFF), Hamanatto belongs to a traditional category known as Shiokara Natto.

Unlike sticky natto, Shiokara Natto is produced by inoculating cooked soybeans with koji mold, allowing the mold to grow, then maturing the beans in salt before drying them.

This method produces a firm texture and an intensely savory flavor rather than the sticky strings associated with modern natto.

The distinction is also reflected in Japan’s official food classification.

The Standard Tables of Food Composition in Japan, published by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), classify Temple Natto (Teranatto), Shiokara Natto, and Hamanatto within the same traditional food group.

These official sources demonstrate that Hamanatto is not simply another regional variation of natto.

It represents a separate branch of Japanese fermentation history that has developed over many centuries.

For chefs, this distinction is important.

Sticky natto is generally eaten as a complete food.

Hamanatto is used more like an aged seasoning, adding depth and complexity in much the same way that anchovies, bottarga, or aged cheeses enrich a dish.

Although both are made from soybeans, they belong to different fermentation traditions.

The Story Begins in Ancient China

The roots of Hamanatto reach far beyond Japan.

Its story begins in ancient China, where fermented soybeans had already become an established food long before similar techniques appeared in Japan.

The earliest detailed description survives in Qimin Yaoshu , an agricultural encyclopedia compiled during China’s Northern Wei dynasty in the sixth century.

The book records the production of chi —salted fermented soybeans that are widely regarded as the ancestor of East Asia’s Shiokara Natto traditions.

What makes this text remarkable is not simply its age but its extraordinary level of detail.

The soybeans were first cooked and carefully cooled before being transferred into a specially prepared fermentation room.

The room was tightly sealed to protect the beans from sudden changes in temperature, insects, and contamination.

Workers monitored the fermentation by inserting their hands into the center of the soybean pile.

The ideal temperature, the text explains, should feel similar to the warmth beneath a person’s arm.

If the beans became too hot, they spoiled.

If they became too cold, fermentation slowed.

The beans were turned repeatedly to maintain an even temperature.

A white coating appeared first, followed by yellow koji mold.

Only after this carefully controlled fermentation were the beans washed, salted, matured, and finally dried.

Even by modern standards, the process reveals an impressive understanding of fermentation management.

Rather than relying on chance, the makers controlled temperature, moisture, airflow, and timing with remarkable precision.

Many of these principles remain fundamental to traditional Hamanatto production today.

The sixth-century Qimin Yaoshu contains one of the earliest detailed descriptions of salted fermented soybeans.

From China to Japan

Historical evidence strongly suggests that the knowledge of making fermented soybeans reached Japan alongside Buddhism during the sixth century.

As Buddhist monks, scholars, and craftsmen traveled from the Asian continent, they introduced far more than religious teachings.

Writing systems, architecture, medicine, agricultural knowledge, and food preservation techniques all accompanied this cultural exchange.

Among these technologies was the fermentation of soybeans using koji mold.

Although no surviving document records the exact moment this technique arrived in Japan, historians generally agree that Buddhist temples played a central role in preserving and transmitting these methods.

Within temple kitchens, Chinese fermentation practices gradually adapted to Japan’s climate, locally grown soybeans, and culinary traditions.

Over time, what had once been known simply as chi (豉) evolved into the Japanese tradition of Shiokara Natto.

Among the few surviving examples of this ancient lineage is Hamanatto.

Its continued production offers a rare opportunity to experience a fermentation method whose origins can be traced back nearly fifteen centuries.

Why This History Still Matters

For many traditional foods, history is little more than a marketing story.

For Hamanatto, history explains its very existence.

Every stage of its production—from cultivating koji to months of salt maturation—reflects techniques refined through centuries of observation and craftsmanship.

Its value does not lie simply in being old.

It lies in preserving a fermentation tradition that has survived political change, technological innovation, and changing tastes while remaining remarkably faithful to its origins.

Understanding where Hamanatto came from allows us to appreciate not only its flavor but also the generations of artisans who ensured that this rare culinary heritage would endure.

The story, however, is far from over.

In the next chapter, we follow Hamanatto into medieval Japan, where historical records begin to reveal the people, places, and documents that shaped its identity.

How Hamanatto Became Part of Japanese History

The Enshū region of present-day western Shizuoka became the center of Hamanatto production.　　　　　　　　　　　　　　　　　　　　　　（Map data from Rekichizu）

From Chi to Kuki

When fermented soybeans first arrived in Japan, they were not known as natto.

Instead, historical documents referred to them using the Chinese character 豉, pronounced chi in Chinese. This word described salted fermented soybeans made with mold rather than the sticky fermentation familiar today.

One of the earliest official references appears in the Yōrō Code, enacted in 718, where chi was recorded among foods managed within the imperial administrative system. By this time, the technique had already become established in Japan.

More than two centuries later, the Wamyō Ruijushō, a Japanese dictionary compiled around 934, assigned the native reading kuki to the same Chinese character.

Although the pronunciation had changed, the food itself had not.

It remained a preserved soybean product created through koji fermentation and salt maturation.

Over time, the imported Chinese food gradually became part of Japan’s own culinary culture.

When Did the Word “Natto” Appear?

Many people assume the word natto has always referred to sticky fermented soybeans.

Historical evidence suggests otherwise.

One of the earliest literary works to use the word natto referred to fermented soybeans prepared in Buddhist temples rather than the sticky product commonly eaten today.

Food historians generally agree that these temple-made products belong to the tradition now called Shiokara Natto.

This explains why Japan eventually developed two entirely different foods sharing the same name.

Sticky natto is produced with Bacillus subtilis, creating its familiar strings and aroma.

Hamanatto, by contrast, belongs to the much older Shiokara Natto tradition, beginning with Aspergillus oryzae and followed by prolonged salt maturation.

Although both foods start with soybeans, their microorganisms, production methods, textures, and culinary uses are fundamentally different.

The term “Chi” (fermented soybeans) appears in the 10th-century Japanese dictionary Wamyō Ruijushō, where it is given the Japanese reading “Kuki”. This is one of the earliest written records showing that Chinese fermented soybeans had already been incorporated into Japanese food culture.

Officially Classified as Shiokara Natto

Modern government publications preserve this historical distinction.

The Ministry of Agriculture, Forestry and Fisheries (MAFF) explains that Hamanatto belongs to Shiokara Natto, a traditional fermented soybean food produced by growing koji on cooked soybeans before maturing them in salt and drying them.

The Ministry of Education, Culture, Sports, Science and Technology (MEXT) reaches the same conclusion in the Standard Tables of Food Composition in Japan, where Temple Natto, Shiokara Natto, and Hamanatto are listed within the same traditional food category.

These independent government sources support what historians have long recognized.

Hamanatto is not simply another variety of natto.

It represents one of Japan’s oldest surviving soybean fermentation traditions.

The Earliest Historical Records

As Japan entered the Muromachi period, documentary evidence becomes increasingly clear.

One of the earliest surviving references appears in the Inryōken Nichiroku.

In an entry dated 1490, fermented soybeans known as Kara Natto from the Enshū region were presented to the Ashikaga shogunate.

Although the document does not yet use the modern name Hamanatto, historians regard it as important evidence that this style of fermented soybean had already become a respected specialty of western Shizuoka.

The fact that it was offered to the shogunate is significant.

Regional foods presented to military rulers were expected to represent exceptional quality and local craftsmanship.

Hamanatto’s predecessor had already earned that reputation.

A More Detailed Description in 1557

The historical picture becomes even clearer in the diary of court noble Yamashina Tokitsugu.

His journal, Tokitsugukyōki , contains an entry from 1557 describing fermented soybeans produced in Enshū.

Unlike earlier references that merely acknowledge the existence of the product, this document indicates that production methods were already well established.

By the middle of the sixteenth century, Hamanatto was no longer an experimental food or a newly imported technique.

It had become a mature regional craft maintained by experienced producers.

This continuity is one of the reasons Hamanatto remains historically significant today.

 Court diaries from the sixteenth century provide valuable evidence for the history of Hamanatto.

The First Printed Use of the Name “Hamanatto”

While earlier documents describe the food, the name Hamanatto itself appears later.

The earliest widely recognized printed example is found in Honchō Shokkan , published in 1697.

This encyclopedic work on Japanese foods records Hamananatto as a regional specialty.

Because Honchō Shokkan sought to document foods from across Japan, its inclusion demonstrates that Hamanatto had already become known beyond its place of production.

For historians, this publication marks an important milestone.

Earlier documents prove the tradition existed.

Honchō Shokkan preserves the name that continues to identify it today.

Tokugawa Ieyasu and the Hamana Region

No discussion of Hamanatto’s history would be complete without mentioning Tokugawa Ieyasu.

During the years he governed Hamamatsu, the region became one of the political and military centers of eastern Japan.

Historical materials published by the City of Hamamatsu describe Hamanatto as one of the local foods associated with the area’s culinary heritage during this period.

Whether eaten directly, carried during travel, or used to season simple meals, foods like Hamanatto offered practical advantages.

They were compact, shelf-stable, and rich in flavor—qualities that were especially valuable long before refrigeration.

Although many details of daily life have been lost to history, Hamanatto clearly formed part of the regional food culture that surrounded one of Japan’s most influential leaders.

A Tradition That Survived

Many traditional foods survive only in written records.

Hamanatto survived because generations of artisans continued making it.

Despite enormous changes in Japanese society over the centuries, the essential process remained remarkably consistent.

Soybeans.

Koji.

Salt.

Time.

Patience.

Those same elements still define authentic Hamanatto today.

The story, however, does not end with history.

Modern science is now helping explain why this ancient fermentation creates such extraordinary depth of flavor.

That is where we turn next.

Why Hamanatto Still Matters Today

 A small amount of Hamanatto can transform an entire dish with concentrated umami.

The Science Behind Hamanatto’s Flavor

History explains where Hamanatto came from.

Science explains why it tastes the way it does.

The fermentation of Hamanatto begins with koji mold (Aspergillus oryzae), one of the most important microorganisms in Japanese food culture. The same mold is also used to produce sake, soy sauce, and miso.

As the koji grows across the cooked soybeans, it releases enzymes that gradually break down proteins into peptides and free amino acids.

Among these amino acids is glutamic acid, one of the primary compounds responsible for the sensation known as umami.

This transformation does not happen overnight.

It requires time, careful temperature control, and the experience of skilled artisans.

After the koji stage, the beans mature in salt. During this period, salt-tolerant microorganisms continue to shape the flavor, producing organic acids and aromatic compounds that add complexity without overwhelming the natural taste of the soybeans.

The result is a food that is not simply salty.

It is layered, balanced, and deeply savory.

More Than a Traditional Food

Many traditional foods survive because people feel nostalgic about them.

Hamanatto has survived because it remains useful.

Its intense flavor allows chefs to season food with only a small quantity.

Instead of masking ingredients, it enhances them.

This is why many people compare its culinary role—not its flavor—to ingredients such as:

• Parmigiano Reggiano
• Anchovies
• Bottarga
• Chinese fermented black beans
• Traditional fish sauce

Each is used sparingly.

Each contributes depth rather than volume.

Hamanatto belongs naturally in this family of ingredients.

Traditional fermentation can inspire modern cuisine.

A Rare Ingredient in Modern Cuisine

Today, only a small number of producers continue making authentic Hamanatto using traditional methods.

Unlike soy sauce or miso, it has never become a mass-produced commodity.

That rarity is not the result of marketing.

It is the natural consequence of a process that demands patience, craftsmanship, and time.

For chefs searching for ingredients with genuine provenance, Hamanatto offers something increasingly uncommon:

• a documented history spanning more than a millennium,
• traditional fermentation techniques preserved across generations,
• naturally developed umami,
• and a story that connects ancient East Asia with contemporary gastronomy.

In an era when many foods are standardized, Hamanatto remains unmistakably regional.

Looking Toward the Future

Interest in fermentation is growing around the world.

Restaurants now make their own miso.

Koji has become the subject of scientific research and culinary experimentation.

Ancient preservation techniques are inspiring new approaches to modern cooking.

Within this renewed appreciation for fermentation, Hamanatto deserves greater recognition.

Not because it is rare.

Not because it is old.

But because it represents a continuous tradition of craftsmanship that has survived for nearly fifteen centuries.

Every batch reflects countless small decisions made by experienced hands.

Every bean carries knowledge passed from one generation to the next.

For chefs, Hamanatto is more than an ingredient.

It is a reminder that some of the world’s most remarkable flavors cannot be rushed.

Conclusion

At first glance, Hamanatto appears to be simply another regional specialty from western Japan.

Its true story is far more remarkable.

Its roots reach back to the soybean fermentations recorded in sixth-century China.

It evolved within Buddhist food culture after arriving in Japan.

It appears in medieval court diaries, historical encyclopedias, and modern government publications.

Today, despite centuries of political, social, and technological change, it continues to be produced using principles that have changed remarkably little.

Few traditional foods can trace such a clear historical journey while remaining a living part of everyday craftsmanship.

Understanding Hamanatto is not only about discovering an unfamiliar ingredient.

It is about appreciating how culinary knowledge travels across cultures, adapts over generations, and survives through the dedication of people who continue to value quality over speed.

Perhaps that is why Hamanatto still feels so relevant today.

Its greatest strength is not its age.

It is the timeless idea that extraordinary flavor is worth waiting for.

References

Historical Sources

• Qimin Yaoshu , Northern Wei Dynasty, 6th century.
• Yōrō Code , 718.
• Wamyō Ruijushō , c. 934.
• Inryōken Nichiroku , 1490.
• Tokitsugukyōki , 1557.
• Honchō Shokkan , 1697.

Government Publications

• Ministry of Agriculture, Forestry and Fisheries (Japan). Introduction to Japanese Fermented Foods.
• Ministry of Agriculture, Forestry and Fisheries (Japan). Traditional Japanese Fermented Foods.
• Ministry of Education, Culture, Sports, Science and Technology (Japan). Standard Tables of Food Composition in Japan.
• City of Hamamatsu. Historical materials concerning Tokugawa Ieyasu and Hamanatto.

Scientific References

• Studies on Aspergillus oryzae in traditional Japanese soybean fermentation.
• Research on microbial communities in Shiokara Natto and related fermented soybean products.
• Studies on free amino acids and umami compounds in fermented soy foods.

Continue Exploring Hamanatto

If you’re interested in traditional Japanese fermentation, you may also enjoy:

• What Is Hamanatto?
• How Hamanatto Is Made
• Hamanatto vs. Natto: What’s the Difference?

Chef’s Note

The finest ingredients are often those that remain quietly rooted in their place of origin.

Hamanatto is one of them.

Made by only a handful of producers and shaped by centuries of craftsmanship, it offers more than flavor alone. It carries a story of cultural exchange, patient fermentation, and the enduring pursuit of umami.

Whether you are a chef, food historian, or simply someone who loves discovering authentic ingredients, Hamanatto invites you to experience a tradition that has been carefully preserved for generations.