Food · Fermented foods

Nagaimo (Chinese Yam / Japanese Long Yam)

ながいも (Nagaimo)

Also known as: Nagaimo, Chinese yam, Japanese long yam, Dioscorea polystachya, Dioscorea opposita, 長芋, Yamatoimo (Yamato yam, distinct cultivar), Ichoimo (ginkgo yam, distinct cultivar)

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At a glance

Category	Food
Japanese labeling name	ながいも
Common Japanese notations	ながいも, 長芋, ナガイモ, 山芋, 大和芋 (yamatoimo, distinct cultivar), いちょう芋 (ichoimo, distinct cultivar)
Origin	Long yam / Chinese yam (Dioscorea polystachya, formerly D. opposita); the volume cultivated yam in Japan; principal modern production regions Aomori (the volume leader at ~40-50% of domestic supply, particularly Towada area), Hokkaido, Nagasaki, Chiba; multiple cultivars including straight nagaimo, yamatoimo (Yamato yam, fan-shaped), and ichoimo (ginkgo-leaf-shaped)
Typical functions	Tororo (grated yam) — the volume retail and foodservice category, Fresh slicing (yamaimo no tanzaku, raw shredded yam in Japanese izakaya cuisine), Okonomiyaki binder ingredient (volume processed-food application), Yamatoimo as Japanese confectionery (joyo manju, kanten yokan binder), Industrial freeze-dried yamaimo powder (food ingredient), Premium gift retail (Aomori brand, regional varieties)
Regulatory status in Japan	Nagaimo follows standard agricultural product labeling. Cultivar disclosure (nagaimo / yamatoimo / ichoimo) is significant for premium positioning. Origin disclosure (Aomori volume leader, Hokkaido, Nagasaki) is essential. Yam (yamaimo) is a JAS-recommended-disclosure allergen — oral allergy syndrome reactions are documented and disclosure is standard practice for processed products.

Nagaimo (ながいも) — long yam (Dioscorea polystachya, formerly D. opposita) — is the volume cultivated yam in Japan and the foundation of the mass-market tororo (grated yam) retail and foodservice category. While jinenjo (Japanese wild yam) commands ultra-premium positioning, nagaimo is the practical volume choice for most yam OEM applications. Aomori Prefecture dominates domestic production (approximately 40-50% of supply, particularly the Towada area), with Hokkaido, Nagasaki, and Chiba as major secondary regions. The OEM applications are diverse and substantial: as the foundation of fresh and frozen tororo retail, as a fresh raw ingredient for yamaimo-no-tanzaku and izakaya foodservice, as a binder ingredient for okonomiyaki and other processed foods (volume application), as the basis of yamatoimo (fan-shaped cultivar) for traditional Japanese confectionery (joyo manju, kanten yokan), and as freeze-dried yamaimo powder for industrial food ingredient supply. Three principal cultivar groups exist: standard nagaimo (cylindrical 30-50cm × 5-7cm), yamatoimo (大和芋, fan/fist-shaped, intermediate viscosity, traditional confectionery use), and ichoimo (いちょう芋, ginkgo-leaf-shaped, premium kaiseki use).

Classification

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Product applications

Functions

Flavoring

Regulatory tags

Culinary ingredient

Origin

Plant-derived

Used in (typical product categories)

Finished-product categories that commonly include this ingredient in Japanese-market formulations.

Fresh whole nagaimo retail (volume retail, with origin disclosure — Aomori, Hokkaido, Nagasaki)
Cut and vacuum-packed nagaimo (convenience retail format)
Frozen tororo / grated yam (major convenience format)
Yamatoimo (fan-shaped cultivar) for traditional confectionery
Ichoimo (ginkgo-leaf-shaped cultivar) for premium foodservice
Freeze-dried yamaimo powder (industrial ingredient)
Tororo-soba ready-meal retail (using nagaimo)

What it is

Nagaimo is Dioscorea polystachya (formerly classified as D. opposita), Chinese yam or Japanese long yam, originating from China and well-established in Japan since ancient times. Modern domestic production has developed sophisticated cultivar diversity for different positioning categories.

Major cultivars: (1) Standard nagaimo — cylindrical, 30-50cm × 5-7cm, the volume cultivar. Aomori Towada area is the dominant production region. Lower viscosity than jinenjo, milder flavor, suitable for volume tororo retail. (2) Yamatoimo (大和芋) — the Yamato area cultivar, fan-shaped or fist-shaped, intermediate viscosity, distinctly suited to traditional Japanese confectionery use (joyo manju binder, kanten yokan structure). Traditional Yamato region (Nara Prefecture) is the historical origin, with modern production also in other regions. (3) Ichoimo (いちょう芋) — ginkgo-leaf-shaped, a regional Saitama and Gunma cultivar, premium kaiseki and gift retail positioning.

Nutritionally, raw nagaimo per 100g provides 64 kcal, 2.2g protein, 0.3g fat, 13.9g carbohydrates with 1.0g dietary fiber. Mineral content includes K 430mg, Mg 17mg, P 27mg per 100g. Yamatoimo is more nutrient-dense (higher protein, more minerals) than nagaimo.

Industrial supply: Aomori at ~40-50% domestic share is the volume leader (Towada area is the established production heartland). Hokkaido, Nagasaki (Shimabara peninsula), and Chiba follow. Total domestic production exceeds 150,000 tonnes annually. Significant export volume to Taiwan and other markets exists, with Japan-origin premium positioning.

Typical uses in Japanese products

Tororo (grated yam) — the volume retail and foodservice category. Fresh whole nagaimo for home grating, frozen tororo retail packs (convenience format with growing share), and tororo-soba and tororo-meshi foodservice are all major applications. Lower viscosity than jinenjo but adequate for mainstream tororo positioning at substantially lower cost.

Yamaimo-no-tanzaku and izakaya raw applications — fresh nagaimo cut into thin julienne strips, served raw with soy sauce, wasabi, or ume sauce. Established izakaya foodservice signature.

Okonomiyaki binder — grated nagaimo or yamatoimo is added to okonomiyaki batter to provide structure and lightness. Okonomiyaki is a major Japanese cuisine category and this is a substantial volume application.

Traditional Japanese confectionery — yamatoimo (fan-shaped cultivar specifically) is essential for joyo manju (a premium Japanese steamed bun), kanten yokan structure, and other traditional Japanese pastries (wagashi). The cultivar produces unique gel-forming and binding properties when grated.

Industrial freeze-dried yamaimo powder — produced for food ingredient supply, used in noodles (some yamaimo-soba and yamaimo-udon SKUs), confectionery, and processed-food applications.

Premium gift retail — Aomori Towada nagaimo, Saitama ichoimo, and traditional Yamato yamatoimo are established premium gift categories.

For OEM: volume fresh nagaimo retail packs (Aomori-origin verifiable for premium positioning), frozen tororo retail OEM (major growth category), yamatoimo for traditional confectionery binder supply, ichoimo for premium foodservice and gift retail, freeze-dried yamaimo powder ingredient supply, and tororo-soba ready-meal retail OEM.

Regulatory classification in Japan

Standard agricultural product labeling. Cultivar disclosure (nagaimo vs yamatoimo vs ichoimo) is essential for premium positioning.

Origin region disclosure: Aomori (Towada area), Hokkaido, Nagasaki, Chiba, Yamato area (Nara) for yamatoimo, Saitama/Gunma for ichoimo.

Yamaimo allergen disclosure: yamaimo (jinenjo, nagaimo, yamatoimo, ichoimo collectively) is a JAS-recommended-disclosure allergen. Standard practice is to disclose yamaimo content in processed products.

Aomori Towada nagaimo regional brand: established consumer recognition though not formally GI-registered.

Regulatory classification in other markets

EU	Imported as Chinese yam or Japanese yam. No mandatory allergen disclosure but yam recognized as oral allergy syndrome trigger. Established export market for nagaimo.
USA	Imported under FDA standard food procedures. Established in Japanese-cuisine specialty channels. Frozen tororo and freeze-dried yamaimo are export-friendly formats.
China	Imported under GACC rules. China is itself a major Chinese yam producer. Japanese-origin Aomori nagaimo positioned as premium specialty.
Korea	Imported as Japanese specialty. Korea has its own ma (마, yam) culture. Japanese-origin nagaimo and yamatoimo positioned as specialty imports.

Example products

Example finished products will be added after verification of cultivar (nagaimo / yamatoimo / ichoimo), origin (Aomori / Hokkaido / Nagasaki / other), and target product format.

All brand names and product names referenced anywhere on this site are the property of their respective owners. Example entries are provided for informational purposes only and do not imply endorsement.

Related ingredients

Used in similar product applications

Other ingredients commonly used in the same finished-product families.

Sharing similar functions

Ingredients that overlap on functional benefit tags.

From the same origin

Other ingredients that share an origin classification.

FAQ for OEM buyers

Q. What's the difference between nagaimo, yamatoimo, and ichoimo for OEM positioning?

All three are cultivars of Dioscorea polystachya but with distinct characteristics and positioning: (1) Standard nagaimo — cylindrical, 30-50cm × 5-7cm, the volume cultivar (Aomori Towada is the production heartland). Lower viscosity, milder flavor, broad applications. Best for volume fresh retail, frozen tororo, izakaya yamaimo-no-tanzaku, and as a general processed-food binder. (2) Yamatoimo (大和芋) — fan-shaped or fist-shaped, originally Yamato area (Nara Prefecture) cultivar, with distinctly higher protein and intermediate viscosity. Traditional and indispensable for joyo manju (Japanese steamed bun), kanten yokan structure, and other traditional wagashi confectionery. The unique binding and gel-forming properties when grated are essential for these applications. Yamatoimo is also used in premium tororo. (3) Ichoimo (いちょう芋) — ginkgo-leaf shape (the name 'ginkgo yam' refers to the leaf-like shape of the tuber), Saitama and Gunma regional cultivar, premium kaiseki and gift retail positioning. The shape allows distinctive presentation in formal cuisine. For OEM positioning: standard nagaimo for volume retail and processed-food applications; yamatoimo specifically for traditional Japanese confectionery (joyo manju, etc.) — substituting standard nagaimo will not produce equivalent results; ichoimo for premium kaiseki and regional gift retail.

Sources · Last reviewed: 2026-04-28

Editorial — Japan nagaimo cultivar positioning reference
MAFF cultivar registration database

References

MEXT Standard Tables of Food Composition — ながいも各形態
Aomori Towada nagaimo production region reference
Editorial — Japan yam cultivar landscape reference

Last updated: 2026-04-28. Ingredient entries are reviewed at least annually against current regulatory listings.