Dioscorea opposita

Nagaimo
Segment of a Dioscorea opposita tuber
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
Order:	Dioscoreales
Family:	Dioscoreaceae
Genus:	Dioscorea
Species:	D. opposita
Binomial name
Dioscorea opposita Thunb.

Grated Dioscorea opposita (Japanese tororo)

Tororo blackbean udon from Tamba (丹波の黒豆とろろうどん)

Dioscorea opposita (nagaimo, yamaimo, Chinese yam, Japanese mountain yam, Korean yam; syn. D. batatas, D. oppositifolia) is a type of yam (Dioscorea) that may be eaten raw.^{[verification needed]}

Dioscorea opposita is an exception to the rule that yams must be cooked before consumption (due to harmful substances in the raw state). In Japanese cuisine, it is eaten raw and grated, after only a relatively minimal preparation: the whole tubers are briefly soaked in a vinegar-water solution, to neutralize irritant oxalate crystals found in their skin. The raw vegetable is starchy and bland, mucilaginous when grated, and may be eaten plain as a side dish, or added to noodles.

Dioscorea opposita is used in the Japanese noodle dish tororo udon/soba. The grated nagaimo is known as tororo (in Japanese). In tororo udon/soba, the tororo is mixed with other ingredients that typically include tsuyu broth (dashi), wasabi, and green onions. Jinenjo (Dioscorea japonica, also called wild yam) is related variety of Japanese yam that is used as an ingredient in soba noodles.

Names

In Chinese it is known as huái shān (淮山), shān yào (山药), or huái shān yào (淮山药).

In Japanese, it is known as yamaimo (kanji: 山芋; hiragana: やまいも). Furthermore, yamaimo is classified into nagaimo (lit. 'long yam'; kanji: 長芋; hiragana: ながいも), ichōimo (lit. 'ginkgo-leaf yam'; kanji: 銀杏芋; hiragana: いちょういも), or yamatoimo (lit. Yamato yam; kanji: 大和芋; hiragana: やまといも), depending on root shapes. Jinenjyo (lit. wild yam; kanji: 自然薯; hiragana: じねんじょ) is another kind of Dioscorea opposita, which is native to fields and mountains in Japan.

In Korea it is called ma (hangul: 마; hanja: 麻).

In Vietnam, the yam is called củ mài or khoai mài. When this yam is processed to become a medicine, the yam is called hoài sơn or tỳ giải.

Non-food uses

The jelly-like substance made from grating the yam, tororojiru (Japanese: とろろ汁), is often served in, or alongside, a number of other dishes. Interestingly, perhaps, this was widely used in the Edo period as a personal lubricant for sexual activities,^{[citation needed]} and it was thus considered improper for it to be eaten by a woman. This aversion also derives from the loud slurping sound one makes when eating it, which is considered to be un-ladylike.^[1]

Traditional uses

The tuber is also used (often in dried form) in traditional Chinese medicine and Chinese herbology.

Shanyao root, 山藥, Radix Dioscoreae oppositae, falls within the Chinese herbal medicine category of Tonify Qi materia medica.^[2][3] Within this category it has specialized and important properties which make it one of the most important and commonly used materia medica in the Chinese medicine repertoire. As a tonifying herb which enters the kidney organ (Zang) and/or channel (Jing), its role is fundamental, in accordance with the dictum that "the kidney is the root of Yin and Yang of all the organs (Zang-fu). Shanyao is classified as being of neutral temperature, an important property which means that, while it significantly tonifies the Qi, it does not at the same time cause Heat; in this way it is able to tonify Qi without injuring the Yin, an important advantage in the treatment of patients with deficient Yin. In this role of tonifying Qi without injuring the Yin it appears in such classical formulas as Liu Wei Di Huang Wan, 六味地黃丸, the Six Flavours Rehmannia Pill, and its many derivative and related formulas.^[4]

Shan Yao is also used in situations where it is necessary to tonify Qi, but where the Yin is not deficient. In this usage it is usually used prepared by dry-frying (chao, 炒), which alters its temperature property to slightly Warm. The slightly Warm property enables it to Warm the spleen, another organ/channel which it enters, enabling the spleen to Dry Dampness, but without injuring Blood, a dimension of the Yin. A typical formula where dry-fried Shan Yao is used to tonify Spleen Qi is Shen Ling Bai Zhu San, 參苓白術散, Ginseng Poria Atractylodes Powder.^[5] It is also frequently found dry-fried in Chinese herbal dermatology^[6] in formulas for treating Blood Dryness where it is necessary to warmly tonify Spleen Qi, to enable it to Transform residual Dampness, but without drying Blood or Yin.

See also

• Yam (vegetable)
• Diosgenin
• Tremella fuciformis

References

1. ^ Dunn, C. and B. Torigoe (1969). The Actors Analects. New York: Columbia University Press. p51.
2. ^ Bensky, Clavey, Stöger and Gamble, Chinese Herbal Medicine: Materia Medica, Seattle, 2004, p. 723 ff
3. ^ Xu and Wang, Chinese Materia Medica: Combinations and Applications, 2002, p. 526 ff
4. ^ Scheid, Bensky, Ellis & Barolet, Chinese Herbal Medicine: Formulas and Strategies, Seattle, 2009, p. 365 ff.
5. ^ Scheid, Bensky, Ellis & Barolet,Chinese Herbal Medicine: Formulas and Strategies, Seattle, 2009, p. 314 ff.
6. ^ Xu, Dermatology in Traditional Chinese Medicine, 2004

External links

• Dioscorea batatas - Decne. (Plants For A Future)
• Dioscorea opposita (Australian New Crops)
• Dioscorea batatas (Australian New Crops)