Dioscorea alata – also called purple yam, ube (/ˈuːbɛ,-beɪ/), or greater yam, among many other names – is a species of
yam (a
tuber). The tubers are usually a vivid
violet-
purple to bright
lavender in color (hence the common name), but some range in color from cream to plain white. It is sometimes confused with
taro and the Okinawa sweet potato beniimo (紅芋) (Ipomoea batatas cv.
Ayamurasaki), however D. alata is also grown in Okinawa. With its origins in the Asian
tropics, D. alata has been known to humans since ancient times.[3]
Names
Because it has become naturalized following its origins in Asia, specifically the
Philippines, through tropical South America, and the southeastern U.S., D. alata is referred to by many different names in these regions. In English alone, aside from purple yam, other common names include ten-months yam, water yam, white yam, winged yam, violet yam, Guyana arrowroot, or simply yam.[3]
History of cultivation
This article is missing information about wild relatives (D. nummularia, D. transverse, and D. hastifolia; progenitor unknown) [doi:10.1111/boj.12374]). Please expand the article to include this information. Further details may exist on the
talk page.(October 2021)
Dioscorea alata is one of the most important staple crops in
Austronesian cultures. It is one of various species of yams that were domesticated and cultivated independently within
Island Southeast Asia and
New Guinea for their starchy
tubers, including the round yam (Dioscorea bulbifera), ubi gadong (Dioscorea hispida), lesser yam (Dioscorea esculenta), Pacific yam (Dioscorea nummularia), fiveleaf yam (Dioscorea pentaphylla), and pencil yam (Dioscorea transversa).[4] Among these, D. alata and D. esculenta were the only ones regularly cultivated and eaten, while the rest were usually considered as
famine food due to their higher levels of the toxin
dioscorine which requires that they be prepared correctly before consumption.[5]D. alata is also cultivated more than D. esculenta, largely because of its much larger tubers.[6]
The center of origin of purple yam is in the Philippines, but archaeological evidence suggests that it was exploited in
Island Southeast Asia and
New Guinea before the
Austronesian expansion. Purple yam is believed to be a true
cultigen, only known from its cultivated forms. The vast majority of cultivars are sterile, which restricts its introduction into islands purely by human agency, making them a good indicator of human movement. Some authors have proposed, without evidence, an origin in
Mainland Southeast Asia, but it shows the greatest phenotypic variability in the
Philippines and
New Guinea.[10][11][12]
Based on archaeological evidence of early farming plots and plant remains in the
Kuk Swamp site, authors have suggested that it was first domesticated in the highlands of New Guinea from around 10,000
BP and spread into Island Southeast Asia via the
Lapita culture at around c. 4,000
BP, along with D. nummularia and D. bulbifera. In turn, D. esculenta is believed to have been introduced by the Lapita culture into New Guinea. There is also evidence of an agricultural revolution during this period brought by innovations from contact with Austronesians, including the development of
wet cultivation.[13][14]
However, much older remains identified as being probably D. alata have also been recovered from the
Niah Caves of
Borneo (
Late Pleistocene, <40,000
BP) and the
Ille Cave of
Palawan (c. 11,000
BP), along with remains of the toxic ubi gadong (D. hispida) which requires processing before it can be edible. Although it doesn't prove cultivation, it does show that humans already had the knowledge to exploit starchy plants and that D. alata were native to Island Southeast Asia. Furthermore, it opens the question on whether D. alata is a true species or cultivated much older than believed.[4][15][16][17][18][19]
Purple yam remains an important crop in Southeast Asia, particularly in the
Philippines where the vividly purple variety is widely used in various traditional and modern desserts. It also remains important in
Melanesia, where it is also grown for ceremonial purposes tied to the size of the tubers at harvest time. Its importance in eastern
Polynesia and
New Zealand, however, has waned after the introduction of other crops, most notably the
sweet potato.[6]
Uses
Culinary
Purple yams have edible tubers which have a mildly sweet, earthy and nutty taste, reminiscent of
sweet potatoes or
taro. The violet cultivars, in particular, turn dishes distinctively vivid violet because of the high amount of
anthocyanins.[20] Purple yams are also valued for the
starch that can be processed from them.[3]
Purple yam is most common in
Philippine cuisine (where it is known as ube or ubi). It is widely applied for many Philippine desserts, such as
ube cake,
ube cheesecake and
ube crinkles, as well as an ingredient or flavor for
ice cream,
milk,
donuts,
tarts, jam and other types of
pastries. It is often eaten boiled, baked, or as a sweetened dessert called ube halayá; the latter being a popular ingredient in the iced dessert called halo-halo.[21][22][23] Purple yam desserts have more recently entered the
United States through Philippine cuisine, under the Filipino name "ube". It is particularly popular due to the striking violet-purple color it gives to desserts.[20][21][24]
Purple yam is commonly confused with purple/violet varieties of
sweet potatoes because of their similarities in color, taste, and culinary uses. However, like other yams, purple yam tends to have a moister texture than sweet potatoes. Purple yams also have higher anthocyanin content than sweet potatoes. They can otherwise be used interchangeably in most recipes.[25][26]
Ube halaya (mashed purple yam) from the Philippines
The color of purple varieties is due to various
anthocyanin pigments.[30] The pigments are water-soluble, and have been proposed as possible
food coloring agents.[31]
D. alata is sometimes grown in gardens for its ornamental value.[3]
^Malapa, R.; Arnau, G.; Noyer, J.L.; Lebot, V. (November 2005). "Genetic Diversity of the Greater Yam (Dioscorea alata L.) and Relatedness to D. nummularia Lam. and D. transversa Br. as Revealed with AFLP Markers". Genetic Resources and Crop Evolution. 52 (7): 919–929.
doi:
10.1007/s10722-003-6122-5.
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