The Acidic King.
Oita Prefecture produces 98% of Japan’s **Kabosu**. This citrus fruit is a relative of the yuzu but possesses a sharper acidity and a unique mineral undertone derived from the volcanic soil. In Beppu, the Kabosu is the essential counter-point to the heavy, sulfurous notes of geothermal cooking.
Technical Application
Kabosu juice is used to "chemically cook" raw sashimi and brighten the broth of *Dangojiru* (Flat-noodle soup). Its high citric acid content is often cited locally as an antioxidant, often added to onsen baths for skin clarification.
Botanical Profile: Oita Kabosu
Approx 2.1
High Citric Index
Andosol
Volcanic Ash Soil
Unlike Yuzu, the Kabosu is harvested green to maximize its pungent, mineral-driven juice profile before the sugars fully develop.
Woven Engineering
High flexibility
high-altitude harvest.
Traditional
geometric bases.
The Madake Harvest
Beppu is the leading producer of **Madake** (Giant Timber Bamboo) in Japan. The craft began in the Edo period when pilgrims visiting the hot springs needed durable, lightweight baskets for their laundry and vegetables.
Today, it is the only bamboo craft in Japan designated as a **Traditional National Handicraft**. Artisans split the bamboo into strips as thin as 0.1mm, weaving them into structural meshes that can last over a century.
Heritage Truth: The Thermal Connection
The bamboo is often treated in the geothermal steam of Kannawa to "oil-strip" the bark, a process that makes the fibers resistant to mold—essential in the high-humidity environment of a hot spring city.
The Alchemy of Adaptation.
In Beppu, the produce is a direct response to the **Andosol (Volcanic Ash) soil**. This soil is naturally acidic and high in aluminum, which would stunt many standard crops. However, it is the perfect environment for citrus and specific highland grains that the locals have utilized for centuries.
Kabosu vs. The Sulfur Palate
Because the local geothermal steam can leave a heavy mineral aftertaste, Beppu locals use the **Kabosu** not just as a garnish, but as a chemical balancer. Its high acidity cuts through the "heaviness" of sulfur-steamed proteins, a culinary logic found nowhere else in Japan.
Dangojiru: The Highland Grain Solution
Historically, Beppu’s rocky, volcanic terrain made rice cultivation difficult. Locals adapted by creating **Dangojiru**—flat, hand-pulled wheat noodles. Unlike the refined udon of the plains, this dish is hearty and thick, designed to be paired with the mineral-rich vegetables grown in the local ash-soil.
Oita Terroir Matrix
"We do not fight the acidity of the volcano; we use it to refine the flavor of the forest."
Chemical Archive: Pigment Source
The Sulfur Stitch.
Beppu’s produce isn't just edible or structural—it is wearable. For centuries, local dyers have utilized the **high mineral concentration** of the "Hells" to create textiles. The boiling, mineral-heavy water opens the fibers of the cloth, allowing the earth’s pigments to bind deeply within the fibers..
The most famous is the **Onsen-zome** (Hot Spring Dyeing). Fabric is soaked in the iron-rich waters of the "Blood Pond," resulting in a deep, earthy terracotta that carries a slight metallic sheen.
Beyond the color, These textiles are traditionally valued for their resistance to odor and mildew.. The trace sulfur and alum embedded in the threads are said to keep the skin healthy, making these "Thermal Garments" a popular purchase for pilgrims visiting the city for medical *Toji* stays.
Heritage Note: The 100-Year Fabric
Because the minerals act as a natural preservative, Beppu-dyed silk is resistant to the humidity and rot that typically plagues textiles in the Japanese sub-tropics.
Grown from Steam.
While technically a mineral, **Yunohana** (Bath Salts) are harvested like a crop in the Myoban district. They represent the "essence" of Beppu produce—a tangible product created entirely by the tectonic activity beneath the city.
Purchasing Intelligence
Genuine Yunohana must be purchased in the original straw-wrapped packaging to ensure 100% mineral purity. One packet recreates the sensory experience of a Myoban sulfur spring.
Extraction Log: Myoban Alum
Crystalline
Solid Condensate
Aluminum Iron
Sulfate Hydrate
The Yunohana crystals are formed by a 60-day reaction between geothermal gas and Myoban's blue clay substrate—an intangible cultural treasure of Japan.
The Trade Equilibrium.
Mapping the flow of minerals and resources between the volcanic rift zones of Kyushu and the Japanese mainland.
Primary Exports
Yunohana Alum Crystals
The most valuable export. These sulfurous bath salts are shipped to luxury ryokans and pharmacies in Tokyo and Kyoto to replicate the Myoban thermal experience.
Kabosu Concentrates
Because Oita produces 98% of the national yield, Beppu exports thousands of liters of juice and zest to the food processing industries of Osaka.
Madake Bamboo Laths
Raw timber bamboo is exported to architectural firms nationwide for high-end interior design and traditional tea house construction.
Primary Imports
Low-Acidity Grains
Beppu's acidic soil is hostile to premium rice. The city imports high-grade Koshihikari rice from the northern Niigata plains to serve in its local inns.
Structural Timber (Hinoki)
While bamboo is plentiful, large-scale Hinoki Cypress needed for bathhouse structural frames is often imported from the deep forests of Gifu and Kiso.
Refined Ceramics
To complement the rustic bamboo, Beppu imports porcelain and ceramic ware from Arita and Saga to maintain the 'high-style' aesthetic of its thermal ryokans.
"The Beppu trade economy is a delicate balance: exporting the 'fire' of the volcano in mineral form, while importing the 'earth' of the plains to sustain its people."