Dioscorea opposita

Dioscorea opposita

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.

It is known as either nagaimo (kanji: ; hiragana: ながいも) or yamaimo (kanji: ; hiragana: やまいも) in Japanese, depending on root shape. In Chinese it is known as huái shān (), shān yào (), or huái shān yào (). In Korea it is called ma (hangul: 마; hanja: ).

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 cold 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.

Personal lubricant

The jelly-like substance made from grating the yam, tororojiru (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, 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.

Medical uses

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


See also

External links

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