| Chinese yam | |
|---|---|
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Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Dioscoreales |
| Family: | Dioscoreaceae |
| Genus: | Dioscorea |
| Species: | D. polystachya |
| Binomial name | |
| Dioscorea polystachya | |
| Synonyms[1] | |
Dioscorea polystachya orChinese yam (simplified Chinese:山药;traditional Chinese:山藥), also calledcinnamon-vine,[2] is a species of flowering plant in theyam family. It is sometimes calledChinese potato or by its Korean namema.[3][2] It is also calledhuaishan in Mandarin andwàaih sāan inCantonese.
It is a perennial climbingvine, native to East Asia.[3][4] The edibletubers are cultivated largely in East Asia and sometimes used inalternative medicine. This species of yam is unique as the tubers can be eaten raw.[5][6]
This plant grows throughoutEast Asia.[7] It is believed to have been introduced to Japan in the 17th century or earlier.[8] Introduced to theUnited States as early as the 19th century for culinary and cultural uses, it is now considered an invasive plant species.[7][9][10][11] The plant was introduced toEurope in the 19th century during theEuropean Potato Failure, where cultivation continues to this day for the contemporary East Asian food market.[12]
Thebotanical namesDioscorea opposita andDioscorea oppositifolia have been consistently misapplied to Chinese yam.[2][5][11] The nameD. opposita is now an acceptedsynonym ofD. oppositifolia.[13] Botanical works that point out the error may list, e.g.,Dioscorea oppositaauct. as a synonym ofD. polystachya.[2] Furthermore, neitherD. oppositifolia nor the priorD. opposita have been found growing in North America and have no historical range in China or East Asia, since this grouping is exclusively native only to thesubcontinent of India and should not be confused withDioscorea polystachya.[5]
Dioscorea polystachya vines typically grow 3–5 meters (9.8–16.4 ft) long, and can be longer. They twine clockwise. The leaves are up to 11 centimeters (4.3 in) long and wide. They are lobed at the base and larger ones may have lobed edges. The arrangement is variable; they may be alternately or oppositely arranged or borne in whorls.
In the leaf axils appear warty roundedbulbils under 2 centimeters (0.79 in) long. The bulbils are sometimes informally referred to as "yam berries" or "yamberries".[14][15]
New plants sprout from the bulbils or parts of them.
The flowers of Chinese yam arecinnamon-scented.
The plant produces one or more spindle-shaped[5] or cylindrical[11] tubers. The largest may weigh 10 pounds (4.5 kg) and grow one meter (3 ft 3 in) underground.[11]Dioscorea polystachya is more tolerant to frost and cooler climates than other yams, which is attributed to its successful introductions and establishment on many continents.
In Chinese it is known asshānyào (simplified Chinese:山药;traditional Chinese:山藥;lit. 'mountain medicine'),huáishān (怀山;懷山 or淮山),[16] orhuáishānyào (怀山药;懷山藥 or淮山药;淮山藥; 'mountain medicine from Huai', i.e. the Huai Qing Fu (怀庆俯;懷慶俯) region). Rarely, it is also referred to asshǔyù (薯蓣;薯蕷). The yam bulbils are referred to asshanyao dou (山药豆;山藥豆; 'yam bean') orshanyao dan (山药蛋;山藥蛋; 'yam eggs').
In Japan, three groups of this species in cultivation are recognized. The common long, cylindrical type is known asnagaimo (長芋,lit. 'long yam'). Theichōimo (銀杏芋, 'ginkgo-leaf yam') bears a flat,palmate shape, and thetsukune imo (つくね芋) 'meatball yam' is round orglobular.[17][18] The termyamatoimo (大和芋, 'Yamato [Province] yam') is used particularly in theKantō region for theichōimo in the market,[19] but this is confusing since traditionallyyamatoimo has also referred totsukuneimo, especially if produced inYamato Province (nowNara Prefecture).[20] Cultivars of this species (such asyamatoimo) is sometimes called "Japanese mountain yam",[21] though that term should properly be reserved for the nativeDioscorea japonica.[8]
In Korea it is calledma (Korean: 마),sanu (Korean: 산우;Hanja: 山芋),seoyeo (서여;薯蕷), orsanyak (산약;山藥).
In Sri Lanka in Sinhala it is calledwal ala (වැල් අල). It is sometimes called Korean yam.
In Vietnam, the yam is calledcủ mài orkhoai mài. When this yam is processed to become a medicine, the yam is calledhoài sơn ortỳ giải.
In theIlocano of the northern Philippines it is calledtuge.
InLatin American countries it is known as camote del cerro or white ñame.
InManipuri it is called as "Ha".
Creams and dietary supplements made from the relatedDioscorea villosa are claimed to contain human hormones and promoted as a medicine for a variety of purposes, includingcancer prevention and the treatment ofCrohn's disease andwhooping cough. However, according to theAmerican Cancer Society, the claims are false and there is no evidence to support these substances being either safe or effective.[22] Huáishān has also been used in traditional Chinese medicine.[23]
Dioscorea polystachya was introduced to the United States in the 1800s when it was planted as anornamental or food crop. It and other introduced yam species now grow wild there. It is troublesome inGreat Smoky Mountains National Park, where its range is "rapidly expanding", particularly into the Tennessee Valley where different native, hybrid and/or invasive non-native variants ofmorning glory andbindweed as well as invasive kudzu andcuscuta (dodder) have all become problematic and are similar in appearance to the fast-moving and often mishandled tubers.
As Chinese yam and air potatoes continue to destroy entire swaths of gardens and yards though are not yet classified as invasive in these areas, residents seeking to eat the tuber plant their vines in unprotected land while residents seeking removal chop the tops off of vines at ground level and compost or mulch them before realizing this only makes the problem worse and that no weed killers on the market are able to rid a garden or yard of the plant. The newest solution from Florida for people in Florida and surrounding states experiencing harm to their property and wishing a reprieve from these plant pests is to request free Air Potato Beetles. However, the beetles continue to elude Tennesseans due to various government regulations and the lack of others.[11] It is most prevalent in moist habitat types. It is more tolerant of frost than other yams and can occur in temperate climates as far north asNew York.[11][24]
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The tubers ofD. polystachya can be eaten raw (grated or sliced[25]), while most other yams must be cooked before consumption (due to harmful substances in the raw state).[17]
First the skin needs to be removed by peeling (or by scraping off using a hard-bristled brush).[26][27] This may cause a slight irritation to the hand, and wearing a latex glove is advised, but if an itch develops then lemon juice or vinegar may be applied.[27][25]
The peeled wholetubers are briefly soaked in a vinegar-water solution, to neutralize irritantoxalate crystals found in their skin,[17] and to prevent discoloration.[26] The raw vegetable is starchy and bland,mucilaginous when cut or grated,[28][25] and may be eaten plain as a side dish, or added to noodles, etc.
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Chinese yam is referred to asshānyào (山药;山藥), or mountain medicine, in Chinese traditional medicine, or referred to as huáishān (怀山; 懷山 or 淮山) in the culinary usage. The tuber is consumed raw, steamed, ordeep-fried. It is added to savory soups, or can be sweetened with a berry sauce. When used fresh, the tuber is peeled before slicing and using them in stir-fries (mainly in Cantonese cuisine). Oftentimes, Chinese yam can be found sold in prepared, dried slices in dried goods specialty shops. When using the dry ingredient in soups, the slices need to be soaked before adding them to soups to cook.
In Japanese cuisine, both the Chinese yam cultivars and theJapanese yam (often wild foraged) are used interchangeably in dishes. The difference is that thenagaimo tends to be more watery, while the native Japanese yam is more viscous.[29]
Thetororo is the mucilaginouspurée made by grating varieties the Chinese yam (nagaimo,ichōimo,tsukuneimo)[17] or the native Japanese yam.[30] The classic Japanese culinary technique is to grate the yam by grinding it against the rough grooved surface of asuribachi, which is an earthenwaremortar.[31] Or the yam is first grated crudely using anoroshigane grater, and subsequently worked into a smoother paste in thesuribachi using a wooden pestle.[32]
Thetororo is mixed with other ingredients that typically includetsuyu broth (soy sauce anddashi), sometimeswasabi orgreen onions,[33][34] and eaten over rice ormugimeshi [ja] (steam-cooked blend of rice andbarley).[17][35][29]
The tororo poured overraw tuna (maguro) sliced into cubes is calledyamakake, and eaten with soy sauce andwasabi.[33]
Thetororo may also be poured over noodles to maketororoudon/soba.[29] Noodles with grated yam over it is also calledyamakake.[26]
Grated yam is also used asbinding agent in the batter ofokonomiyaki.[29]
Sometimes the grated yam is used as an additive for making the skin of themanjū confection, in which case the product is calledjōyo manjū [ja] (薯蕷饅頭, "yam manjū").[36][37] The yam is also used in the making a regional confection calledkarukan, a specialty of theKyūshū region.[29]
InKorea, there are two main types of Chinese yam: The straight, tube-shaped variant is calledjangma (Korean: 장마;lit. "longma"), whiledanma (Korean: 단마;lit. "shortma") refers to the variant, which grows shorter, cluster-like tubes.[38] Both are used in cooking and the tubers are prepared in a variety of ways. They are most commonly consumed raw, after the skinned roots have been blended with water, milk or yogurt (occasionally with additional honey) to create a nourishing drink known asmajeup (마즙) or "ma juice" (마주스). Alternatively, the peeled tubers are cut into pieces and served—either raw, after cooking, steaming or frying, along with seasoning sauces.
The Chinese yam's growing cycle spans approximately one year, and should be planted between winter and spring. The traditional methods growing it are: using smaller tubers, top cut of bigger tubers or through cuttings of branches. The first two methods can produce 20 cm (7.8 in) long tubers and above. The latter produces smaller tubers (10 cm or 4 in) that are usually replanted for the next year.
Between 7 and 9 months of replanting Chinese yam tubers, their leaves start to get dry (a common fact in plants that grow tubers), which indicates that the tubers are ready for harvest. In home gardens generally only what will be consumed is harvested, with the rest left in the pot in moist soil.[39]
