Food · Fermented foods

Daijo (Water Yam)

だいじょ (Daijo)

Also known as: Daijo, Water yam, Greater yam, Dioscorea alata, ダイジョ, Beni-daijo (purple variety)

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At a glance

Category	Food
Japanese labeling name	だいじょ
Common Japanese notations	だいじょ, ダイジョ, 大薯, 紫だいじょ
Origin	Water yam (Dioscorea alata); subtropical species, principal modern domestic production in Okinawa and Kagoshima (Amami Islands and southern Kyushu); much smaller volume than nagaimo; purple-flesh varieties (beni-daijo / 紅だいじょ) overlap with the Okinawa beni-imo / murasaki-imo positioning
Typical functions	Okinawan and Amami regional cuisine ingredient, Purple-flesh varieties for anthocyanin-positioned functional food and confectionery, Tropical and subtropical specialty positioning, Foodservice and gift retail in southern Kyushu and Okinawa
Regulatory status in Japan	Standard agricultural product labeling. Daijo overlaps with beni-imo / murasaki-imo positioning when purple varieties are involved. Total domestic volume is small — niche specialty.

Daijo (だいじょ) — water yam (Dioscorea alata) — is a tropical/subtropical yam species widely cultivated globally but with very limited domestic Japanese production, concentrated in Okinawa and Kagoshima (Amami Islands and southern Kyushu). The OEM positioning is niche regional specialty: as a southern Kyushu and Okinawa regional cuisine ingredient, as a purple-flesh anthocyanin source (beni-daijo varieties overlap with the broader beni-imo / murasaki-imo functional positioning), and as a specialty regional gift item. The species is distinct from the more familiar nagaimo (Dioscorea polystachya) and jinenjo (Dioscorea japonica) — daijo has a softer, less viscous texture when grated, more carb-forward flavor, and produces dramatically larger tubers (some over 1m long and tens of kilograms). For most Japanese OEM applications nagaimo, jinenjo, or yamatoimo are more appropriate — daijo is best understood as a southern regional specialty.

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 daijo retail (Okinawa and Kagoshima regional)
Purple daijo (beni-daijo) for anthocyanin-positioned products
Local foodservice ingredient supply

What it is

Daijo (Dioscorea alata) is the water yam or greater yam, a tropical/subtropical yam species cultivated extensively in Asia, the Pacific, Africa, and South America. In Japan, cultivation is concentrated in Okinawa and Kagoshima (Amami Islands, mainland southern Kyushu). The species produces very large tubers (some commercial-grade specimens exceed 50cm length and 5kg weight; record-size exceeds 1m and 50kg).

Daijo includes both white-flesh and purple-flesh (beni-daijo) varieties. The purple varieties have anthocyanin content and overlap with the broader beni-imo / murasaki-imo positioning category in Okinawan cuisine.

Nutritionally, raw daijo provides approximately 102 kcal, 2.6g protein, 0.1g fat, 23.5g carbohydrates per 100g. The texture when grated is softer and less viscous than nagaimo or jinenjo.

Total annual Japanese production is small. Most volume is consumed within Okinawa and southern Kyushu regional foodservice and retail; minimal supply reaches mainland mass-market retail.

Typical uses in Japanese products

Okinawan and Amami regional cuisine — boiled, fried, grated, or used in regional dishes including imo-tempura and traditional preparations.

Purple beni-daijo for anthocyanin-positioned products — overlap with beni-imo/murasaki-imo confectionery and functional food category.

Regional foodservice — southern Kyushu and Okinawa restaurants and izakaya use daijo in regional menu items.

Tropical-positioned premium specialty — niche urban gourmet positioning for the larger-tuber, distinct-flavor profile.

For OEM: limited but distinct positions — purple beni-daijo for confectionery and functional food formulations, fresh and frozen daijo for southern Kyushu and Okinawa regional retail, and specialty tropical-positioned restaurant ingredient supply.

Regulatory classification in Japan

Standard agricultural product labeling. Origin disclosure (Okinawa / Kagoshima / Amami) is essential for regional positioning.

Daijo and beni-daijo are not designated allergens, but yam-family allergen disclosure (recommended) applies.

Distinction from sweet potato (beni-imo) and other purple Okinawa products requires clear product naming.

Regulatory classification in other markets

EU	Imported as water yam or greater yam. Established global trade for D. alata.
USA	Imported under FDA standard food procedures. Established in Asian and Caribbean specialty channels.
China	China has its own water yam culture — Japanese-origin daijo is niche specialty.
Korea	Niche specialty positioning.

Example products

Example finished products will be added after verification of variety (white-flesh daijo / purple beni-daijo) and origin region.

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. How does daijo differ from nagaimo or jinenjo for OEM applications?

Daijo (Dioscorea alata) is a tropical/subtropical species distinct from nagaimo (D. polystachya) and jinenjo (D. japonica). Key differences for OEM: (1) Production region — daijo is Okinawa and Kagoshima only, while nagaimo and jinenjo are mainland Japanese. (2) Tuber size — daijo produces dramatically larger tubers (often 5kg+, sometimes tens of kg). (3) Texture when grated — daijo is softer and less viscous than nagaimo or jinenjo (much less suitable for traditional tororo). (4) Variety options — purple beni-daijo provides anthocyanin positioning option that nagaimo lacks. (5) Volume — daijo total domestic supply is much smaller than nagaimo. For OEM positioning: daijo is best for southern Kyushu / Okinawa regional cuisine applications, purple anthocyanin-positioned functional food and confectionery (where beni-daijo competes with beni-imo / murasaki-imo), and specialty tropical-positioned premium retail. For mainstream tororo, mainstream Japanese cuisine, or volume retail applications, nagaimo or jinenjo are more appropriate.

Sources · Last reviewed: 2026-04-28

Editorial — Japan yam family species comparison reference
Okinawa Prefecture daijo production reference

References

MEXT Standard Tables of Food Composition — だいじょ
Okinawa and Kagoshima Amami daijo production reference

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