Dioscorea Opposita rhizome
<p ><i><b>Dioscorea opposita</b></i> (<b>nagaimo</b>, <b>Chinese yam</b>, <b>Korean yam</b>) is a type of <a href="http://en.wikipedia.org/wiki/Yam_(vegetable)" title="Yam (vegetable)" >yam</a>(<i><a href="http://en.wikipedia.org/wiki/Dioscorea" title="Dioscorea" >Dioscorea</a></i>) that may be eaten raw.</p>
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<i>Dioscorea opposita</i> is an exception to the rule that yams must be cooked before consumption (due to harmful substances in the raw state). In <a href="http://en.wikipedia.org/wiki/Japanese_cuisine" title="Japanese cuisine" >Japanese cuisine</a>, it is eaten raw and grated, after only a relatively minimal preparation: the whole <a href="http://en.wikipedia.org/wiki/Tuber" title="Tuber" >tubers</a> are briefly soaked in a vinegar-water solution, to neutralize irritant <a href="http://en.wikipedia.org/wiki/Oxalate" title="Oxalate" >oxalate</a> crystals found in their skin. The raw vegetable is starchy and bland, <a href="http://en.wikipedia.org/wiki/Mucilaginous" title="Mucilaginous" class="mw-redirect" >mucilaginous</a> when grated, and may be eaten plain as a side dish, or added to noodles.</p>
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<i>Dioscorea opposita</i> is used in the Japanese noodle dish <i>tororo <a href="http://en.wikipedia.org/wiki/Udon" title="Udon" >udon</a>/<a href="http://en.wikipedia.org/wiki/Soba" title="Soba" >soba</a></i> and as a binding agent in the batter of <a href="http://en.wikipedia.org/wiki/Okonomiyaki" title="Okonomiyaki" >okonomiyaki</a>. The grated <i>nagaimo</i> is known as <i>tororo</i> (in Japanese). In <i>tororo udon/soba</i>, the <i>tororo</i> is mixed with other ingredients that typically include <i>tsuyu</i> broth (<a href="http://en.wikipedia.org/wiki/Dashi" title="Dashi" >dashi</a>), <a href="http://en.wikipedia.org/wiki/Wasabi" title="Wasabi" >wasabi</a>, and <a href="http://en.wikipedia.org/wiki/Scallion" title="Scallion" >green onions</a>.</p>