Yam (vegetable)
Overview

Yam is the common name for some species in the genus Dioscorea
Dioscorea
Dioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending into temperate climates...

(family Dioscoreaceae
Dioscoreaceae
Dioscoreaceae is a family of monocotyledonous flowering plants, with about 750 species in eight or nine genera. The best-known member of the family is the Yam ....

). These are perennial
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

 herbaceous
Herbaceous
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

 vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s cultivated for the consumption of their starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

y tuber
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...

s in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Latin America
Latin America
Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

 and Oceania
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...

. There are many cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s of yam.

Although the sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

 (Ipomoea batatas) has traditionally been referred to as a yam in parts of the United States and Canada, it is not part of the Dioscoreaceae family.

Although it is unclear which came first, the word yam is related to Portuguese
Portuguese language
Portuguese is a Romance language that arose in the medieval Kingdom of Galicia, nowadays Galicia and Northern Portugal. The southern part of the Kingdom of Galicia became independent as the County of Portugal in 1095...

 inhame or Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

 ñame, which both ultimately derive from the Wolof
Wolof language
Wolof is a language spoken in Senegal, The Gambia, and Mauritania, and is the native language of the Wolof people. Like the neighbouring languages Serer and Fula, it belongs to the Atlantic branch of the Niger–Congo language family...

 word nyam, meaning "to sample" or "taste"; in other African languages
Languages of Africa
There are over 2100 and by some counts over 3000 languages spoken natively in Africa in several major language families:*Afro-Asiatic spread throughout the Middle East, North Africa, the Horn of Africa, and parts of the Sahel...

 it can also mean "to eat", e.g.
Encyclopedia
Top 10 Producers - 2008
(million metric ton)
35.0
6.9
4.8
1.8
0.6
0.3
0.2
0.2
0.2
World Total 50.0
Source:
UN Food & Agriculture Organisation
(FAO)
http://faostat.fao.org/faostat/form?collection=Production.Crops.Primary&Domain=Production&servlet=1&hasbulk=0&version=ext&language=EN

Yam is the common name for some species in the genus Dioscorea
Dioscorea
Dioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending into temperate climates...

(family Dioscoreaceae
Dioscoreaceae
Dioscoreaceae is a family of monocotyledonous flowering plants, with about 750 species in eight or nine genera. The best-known member of the family is the Yam ....

). These are perennial
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...

 herbaceous
Herbaceous
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

 vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s cultivated for the consumption of their starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

y tuber
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...

s in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Latin America
Latin America
Latin America is a region of the Americas where Romance languages  – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...

 and Oceania
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...

. There are many cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s of yam.

Although the sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

 (Ipomoea batatas) has traditionally been referred to as a yam in parts of the United States and Canada, it is not part of the Dioscoreaceae family.

Although it is unclear which came first, the word yam is related to Portuguese
Portuguese language
Portuguese is a Romance language that arose in the medieval Kingdom of Galicia, nowadays Galicia and Northern Portugal. The southern part of the Kingdom of Galicia became independent as the County of Portugal in 1095...

 inhame or Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

 ñame, which both ultimately derive from the Wolof
Wolof language
Wolof is a language spoken in Senegal, The Gambia, and Mauritania, and is the native language of the Wolof people. Like the neighbouring languages Serer and Fula, it belongs to the Atlantic branch of the Niger–Congo language family...

 word nyam, meaning "to sample" or "taste"; in other African languages
Languages of Africa
There are over 2100 and by some counts over 3000 languages spoken natively in Africa in several major language families:*Afro-Asiatic spread throughout the Middle East, North Africa, the Horn of Africa, and parts of the Sahel...

 it can also mean "to eat", e.g. yamyam and doya in Hausa
Hausa language
Hausa is the Chadic language with the largest number of speakers, spoken as a first language by about 25 million people, and as a second language by about 18 million more, an approximate total of 43 million people...

 or "to chew" in Dholuo language of the Luo of Kenya and Northern Tanzania.

The yam is a versatile vegetable which has various derivative products after process, it can be barbecue
Barbecue
Barbecue or barbeque , used chiefly in the United States, Canada, the United Kingdom, New Zealand and Australia is a method and apparatus for cooking meat, poultry and occasionally fish with the heat and hot smoke of a fire, smoking wood, or hot coals of...

d; roasted; fried
Frying
Frying is the cooking of food in oil or another fat, a technique that originated in ancient Egypt around 2500 BC. Chemically, oils and fats are the same, differing only in melting point, but the distinction is only made when needed. In commerce, many fats are called oils by custom, e.g...

; grilled; boiled; smoked and when grated it is processed into a dessert recipe. Yams are the staple crop of the Igbo
Igbo people
Igbo people, also referred to as the Ibo, Ebo, Eboans or Heebo are an ethnic group living chiefly in southeastern Nigeria. They speak Igbo, which includes various Igboid languages and dialects; today, a majority of them speak English alongside Igbo as a result of British colonialism...

 people of Nigeria, in their language it is known as ji, and they commemorate it by having yam festivals known as Iri-ji
New Yam Festival of the Igbo
The New Yam festival of the Igbo is an annual harvest festival by the Igbo people held at the end of the rainy season in early August. The Iwa ji festival is practiced throughout West Africa and other African countries and beyond, symbolizing the conclusion of a harvest and the beginning of the...

or Iwa-Ji depending on the dialect.

Yam tubers can grow up to 1.5 m (4.9 ft) in length and weigh up to 70 kg (154 lb) and 3 to 6 inches high. The vegetable has a rough skin which is difficult to peel, but which softens after heating. The skins vary in color from dark brown to light pink. The majority of the vegetable is composed of a much softer substance known as the "meat". This substance ranges in color from white or yellow to purple or pink in mature yams.

Yams are a primary agricultural commodity in West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

 and New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

. They were first cultivated in Africa and Asia about 8000 BC. Due to their abundance and consequently, their importance to survival, the yam was highly regarded in Nigerian ceremonial culture and used as a vegetable offered during blessings.

Yams are still important for survival in these regions. The tubers can be stored up to six months without refrigeration, which makes them a valuable resource for the yearly period of food scarcity at the beginning of the wet season.

Yams are used as food plants by the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e of some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

 species including Palpifer sordida
Palpifer
Palpifer is a genus of moths of the family Hepialidae. There are 10 described species found in south and east Asia and parts of Mexico.- Species :*P. falkneri - Nepal*P. hopponis - Taiwan*P. madurensis - Madura*P. murinus - India...

.

Preparation

Africa

Yams of African species must be cooked to be safely eaten, because various natural substances in raw yams can cause illness if consumed. (Excessive skin contact with uncooked yam fluids can cause the skin to itch. If this occurs, a quick cold bath or application of red palm oil to the affected part of the body will stop the itching). The most common cooking method in Western
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

 and Central Africa
Central Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....

 is by boiling, frying and roasting the yam.

Preparing boiled yam involves dividing the tuber into round pieces (as you would slice a full cucumber into about 5 circular pieces), then peeling the skin around each cut piece, and boiling the whitish starchy "meat". The older the yam, the smaller the chunks must be cut and the more water it will need to boil. Boiled yam is usually consumed with palm oil (traditional way), pepper sauce, palaver sauce
Palaver sauce
Palaver sauce or Palava sauce is a type of stew widely eaten in West Africa, including Ghana, Liberia, Sierra Leone and Nigeria. The word palaver comes from the Portuguese language and means a talk, lengthy debate or quarrel. It is unclear how this led to the name of the stew...

 or any preferred sauce.

Among the Akan of Ghana, boiled yam can be mashed with palm oil into eto (the yam version if what is known as matoke
Matoke
Matoke, also known as Matooke or Ibitoke , is a meal consisting of steamed green banana and is one of the national dishes of Uganda....

 and served with eggs. The boiled yam can also be pounded with a traditional mortar and pestle to create a thick starchy paste known as Pounded Yam Iyan or Fufu
Fufu
Fufu, , is a staple snack of West and Central Africa. It is a thick paste usually made by boiling starchy root vegetables in water and pounding with a mortar and pestle until the desired consistency is reached...

 which is eaten with traditional sauces such as egusi
Egusi
Egusi seeds are the fat- and protein-rich seeds of certain cucurbitaceous plants. Authorities disagree whether the word is used more properly for the seeds of the colocynth, those of a particular large-seeded variety of the watermelon, or generically for those of any cucurbitaceous plant...

 and palmnut soup.

Another method of consumption is to sun dry the raw yam pieces. When dry, the pieces turn a dark brown color. This is then milled to create a powder known as "elubo" in Nigeria. The brown powder can be prepared with boiling water to create a thick brown starchy paste known as amala
Amala
Amala is a given name in India. It may also refer to:* Amala , a South Indian actress* Amala and Kamala, two girls discovered in 1920, who were raised by wolves in India* Amala , a West African meal...

 which also goes with local soups and sauces.

In big cities and border towns in West Africa, fried yam and pepper sauce is a popular street food and has a similar position as french fries
French fries
French fries , chips, fries, or French-fried potatoes are strips of deep-fried potato. North Americans tend to refer to any pieces of deep-fried potatoes as fries or French fries, while in the United Kingdom, Australia, Ireland and New Zealand, long, thinly cut slices of deep-fried potatoes are...

  and ketchup
Ketchup
Ketchup is a sweet-and-tangy condiment typically made from tomatoes, vinegar, sugar or high-fructose corn syrup and an assortment of...

 elsewhere. Yam balls (the yam version of meat ball) has also gained some popularity in contemporary West African cuisine.

The Philippines

In the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

, the purple ube species of yam (Dioscorea alata), is eaten as a sweetened dessert called "ube halaya", and is also used as an ingredient in another Filipino dessert, halo-halo
Halo-halo
Halo-halo is a popular Filipino dessert that is a mixture of shaved ice and evaporated milk to which are added various boiled sweet beans and fruits, and served in a tall glass or bowl....

.

Vietnam

In Vietnam, the same purple yam is used for preparing a special type of soup canh khoai mỡ or fatty yam soup. This involves mashing the yam and cooking it until very well done.

Indonesia

In Indonesia, the same purple yam is used for preparing desserts. This involves mashing the yam and mixing it with coconut milk and sugar.

Japan

An exception to the cooking rule is the Japanese mountain yam (Dioscorea opposita
Dioscorea opposita
Dioscorea opposita is a type of yam that may be eaten raw....

), known as nagaimo or depending on the root shape.
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
Oxalate
Oxalate , is the dianion with formula C2O42− also written 22−. Either name is often used for derivatives, such as disodium oxalate, 2C2O42−, or an ester of oxalic acid Oxalate (IUPAC: ethanedioate), is the dianion with formula C2O42− also written (COO)22−. Either...

 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.

In Japan, the purple yam is popular as lightly deep fried tempura as well as being grilled or boiled. Additionally, the purple yam is a common ingredient of yam ice cream with the signature purple color.

India

In central parts of India, the yam (or Garadu) is prepared by being finely sliced, seasoned with spices and deep fried. In southern parts of India, the vegetable is a popular accompaniment to fish curry. In Assam
Assam
Assam , also, rarely, Assam Valley and formerly the Assam Province , is a northeastern state of India and is one of the most culturally and geographically distinct regions of the country...

, it is known as Kosu (কচু) and is normally boiled, mashed and lightly seasoned with salt.

Also eaten in India, Dioscorea alata, a purple-pigmented species, is known as ratalu or violet yam.

The West

'Yam powder' is available in the West from grocers specializing in African products, and may be used in a similar manner to instant mashed potato powder, although preparation is a little more difficult because of the tendency to form lumps. The 'yam powder' is sprinkled onto a pan containing a small amount of boiling water, and stirred vigorously. The resulting mixture is served with a heated sauce, such as tomato and chili, poured onto it. To avoid lumps forming, the powder and the water are mixed before putting on the heat, then stirred continuously as the mixture is heating.

Nigeria and Ghana

A Yam Festival is usually held in the beginning of August at the end of the rainy season. A popular holiday in Ghana, the Yam Festival is so named because yam is the most common food in many African countries. Yams are the first crops to be harvested. People offer yams to gods and ancestors first, before distributing them to the villagers. This is their way of giving thanks to the spirits above them.

New Yam Festival (Igbo in South-East, Nigeria)

The New Yam Festival consists of prayers and thanks for the years past. Yam is the main agricultural crop of the Igbos, Idomas, and Tivs. It is the "staple" food of the Igbo people. The New Yam Festival, known as Orureshi in Owukpa in Idoma west and Ima-Ji, Iri-Ji or Iwa Ji in Igbo land is a celebration depicting the prominence of yam in the social and cultural life. The festival is very promiment among all the major tribes in Benue state, mainly around August.

The celebration is followed by various cultural dance with the display of masquerades from different clans or groups. This usually last to very late night. During the occasion is also a moment of reuniting old friends and family members.

Traditionally, there was "The Feast of the New Yam," which was held every year before the harvest began in many Igbo villages prior to colonialism. This feast was held to honor the earth goddess and the ancestral spirits of the clan. New yams could not be eaten until some had first been offered to these powers.

Elsewhere

Historical records in West Africa and of African yams in Europe date back to the 16th century. Yams were taken to the Americas through precolonial Portuguese and Spanish on the borders of Brazil and Guyana, followed by a dispersion through the Caribbean.

The coming of the yams (one of the numerous versions from Maré
Maré
Maré is a commune in the Loyalty Islands Province of New Caledonia, an overseas territory of France in the Pacific Ocean.The commune of Maré is made up of Maré Island and the much smaller Dudun Island, which lie among the Loyalty Islands, to the northeast of New Caledonia's mainland. The settlement...

) is described in Pene Nengone (Loyalty Islands
Loyalty Islands
The Loyalty Islands are an archipelago in the Pacific. They are part of the French territory of New Caledonia, whose mainland is away. They form the Loyalty Islands Province , one of the three provinces of New Caledonia...

 - New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...

)

In many societies yams are so important that one can speak of a 'yam civilization'. Growing the tuber is associated with magic; the best ones must be given to the chief or king; there is a series of myths connected to a divine origin; a farmer may gain a lot of prestige by growing the largest or longest yam.

In Tonga, the ancient names of the months of the year, and the names of the days of the moon-month, were all geared towards the growing of yam. People of ancient times worshiped the yam. Olhuala
Olhuala
Olhuala is a type of yam grown on the island atoll of Fuvahmmulah, Maldives ....

 is a type of local yam that is a staple food in the Maldives
Maldives
The Maldives , , officially Republic of Maldives , also referred to as the Maldive Islands, is an island nation in the Indian Ocean formed by a double chain of twenty-six atolls oriented north-south off India's Lakshadweep islands, between Minicoy Island and...

.

On the Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese island of Rishiri
Rishiri Island
rises out of the Sea of Japan off the coast of Hokkaidō, Japan. The island is formed by the cone-shaped extinct volcanic peak of Mount Rishiri. Along with Rebun and the coastal area of Sarobetsu, Rishiri forms the Rishiri-Rebun-Sarobetsu National Park. The main industries of Rishiri are tourism and...

, yams and yam products are regarded as a folk remedy for the treatment of impotence
Erectile dysfunction
Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

, possibly because of the vegetable's high vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...

 content, but likely because of its evocation of virile phallic imagery, according to the common folk medicine theory of sympathetic medicine
Magical thinking
Magical thinking is causal reasoning that looks for correlation between acts or utterances and certain events. In religion, folk religion, and superstition, the correlation posited is between religious ritual, such as prayer, sacrifice, or the observance of a taboo, and an expected benefit or...

.

Dioscorea rotundata and D. cayenensis

Dioscorea rotundata
Dioscorea rotundata
Dioscorea rotundata, the "white yam", is a species of yam native to Africa. It is one of the most important cultivated yams, along with the Dioscorea cayenensis. It is sometimes known as the "Guinea Yam" D...

, the "white yam", and Dioscorea cayenensis, the "yellow yam", are native to Africa. They are the most important cultivated yams. In the past they were considered two separate species but most taxonomists now regard them as the same species. There are over 200 cultivated varieties between them. The Kokoro
Kokoro (vegetable)
Kokoro is a variety of Dioscorea rotundata yam that are abundant in Western Nigeria, Benin and Togo. Their common use by ethnic groups such as the Yoruba that put heavy pressure on the cultivated land suggest that they have been cultivated since ancient times, since they are the only type of yam...

 variety is important in making dried yam chips.

They are large plants; the vines can be as long as 10 metre. The tubers most often weigh about 2.5 to 5 kg (5.5 to 11 ) each but can weigh as much as 25 kilograms (55.1 lb). After 7 to 12 months growth the tubers are harvested. In Africa most are pounded into a paste to make the traditional dish of "pounded yam" (Kay 1987).

D. alata

Dioscorea alata, called "water yam", "winged yam" and "purple yam" (not to be confused with the Okinawan purple "yam", which is a sweet potato
Sweet potato
The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

), was first cultivated in Southeast Asia. Although not grown in the same quantities as the African yams, it has the largest distribution world-wide of any cultivated yam, being grown in Asia, the Pacific islands, Africa, and the West Indies (Mignouna 2003). In the United States it has become an invasive species in some Southern states.

In the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

 it is known as "ube" and is used as an ingredient in many sweet desserts. In Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

, it is called khoai mỡ and is used mainly as an ingredient for soup. In India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, it is known as ratalu or violet yam. In Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

 it is known as uhi.

Uhi was brought to Hawaii by the early Polynesian settlers and became a major crop in the 19th century when the tubers were sold to visiting ships as an easily stored food supply for their voyages (White 2003).

D. opposita

Dioscorea opposita
Dioscorea opposita
Dioscorea opposita is a type of yam that may be eaten raw....

, "Chinese yam", is native to China. The Chinese yam plant is somewhat smaller than the African, with the vines about 3 meters (10 feet) long. It is tolerant to frost and can be grown in much cooler conditions than other yams. It is now grown in China, Korea, and Japan.

It was introduced to Europe in the 19th century when the potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

 crop there was falling victim to disease, and is still grown in France for the Asian food market.

The tubers are harvested after about 6 months of growth. Some are eaten right after harvesting and some are used as ingredients for other dishes, including noodles, and for traditional medicines (Kay 1987).

D. bulbifera

Dioscorea bulbifera
Dioscorea bulbifera
Dioscorea bulbifera, the Air potato, is a yam species. It is also known as Varahi in Sanskrit, Kaachil in Malayalam and Dukkar Kand in Marathi. The Air potato plant is native to Africa and Asia.-Description:...

, the "air potato", is found in both Africa and Asia, with slight differences between those found in each place. It is a large vine, 6 metres (19.7 ft) or more in length. It produces tubers; however the bulb
Bulb
A bulb is a short stem with fleshy leaves or leaf bases. The leaves often function as food storage organs during dormancy.A bulb's leaf bases, known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is...

ils which grow at the base of its leaves are the more important food product. They are about the size of potatoes (hence the name "air potato"), weighing from 0.5 to 2 kg (1.1 to 4.4 ).

Some varieties can be eaten raw while some require soaking or boiling for detoxification before eating. It is not grown much commercially since the flavor of other yams is preferred by most people. However it is popular in home vegetable gardens because it produces a crop after only four months of growth and continues producing for the life of the vine, as long as two years. Also the bulbils are easy to harvest and cook (Kay 1987).

In 1905 the air potato was introduced to Florida and has since become an invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 in much of the state. Its rapid growth crowds out native vegetation and is very difficult to remove since it can grow back from the tubers, and new vines can grow from the bulbils even after being cut down or burned (Schultz 1993).

D. esculenta

Dioscorea esculenta
Dioscorea esculenta
Dioscorea esculenta, commonly known as the Lesser Yam, is a yam species, but with a smaller corm than most other yams. It is closer in size to a potato or sweet potato. In Vietnam, it is called khoai từ or củ từ.- Taxonomy :...

, the "lesser yam", was one of the first yam species cultivated. It is native to Southeast Asia and is the third most commonly cultivated species there, although it is cultivated very little in other parts of the world. Its vines seldom reach more than 3 meters (10 feet) in length and the tubers are fairly small in most varieties.

The tubers are eaten baked, boiled, or fried much like potatoes. Because of the small size of the tubers, mechanical cultivation is possible; which, along with its easy preparation and good flavor, could help the lesser yam to become more popular in the future (Kay 1987).

D. trifida

Dioscorea trifida
Dioscorea trifida
The climbing perennial vine Dioscorea trifida is a species of yam native to the Caribbean and tropical Central and South America. It is known by a variety of common names, including Indian yam, napi, yampie or yampi, name mapuey, aja, cara doce, and cushcush...

, the "cush-cush yam", is native to the Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...

 region of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 and is the most important cultivated New World
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...

 yam. Since they originated in tropical rain forest
Rainforest
Rainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...

 conditions their growth cycle is less related to seasonal changes than other yams. Because of their relative ease of cultivation and their good flavor they are considered to have a great potential for increased production (Kay 1987).

D. dumetorum

Dioscorea dumetorum, the "bitter yam", is popular as a vegetable in parts of West Africa; one reason being that their cultivation requires less labor than other yams.

The wild forms are very toxic and are sometimes used to poison animals when mixed with bait. It is said that they have also been used for criminal purposes (Kay 1987).

Nutritional value

Yam provides around 110 calories per 100 grams of product. Yam is high in vitamins C and B6, potassium, manganese and dietary fiber while being low in saturated fat and sodium. A product that is high in potassium and low in sodium is likely to produce a good potassium-sodium balance in the human body, and so protects against osteoporosis and heart disease.

Yam products generally have a lower glycemic index
Glycemic index
The glycemic index, glycaemic index, or GI is a measure of the effects of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream have a high GI; carbohydrates that break down more slowly, releasing glucose more...

 than potato products.

The African yam (Dioscorea sp) contains thiocyanate which was implicated by one author as potentially important in sickle cell anemia, an effect that remains scientifically unsubstantiated.

Nigerian language terms

The word "nyam" attributed to the Wolof people
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

 here actually comes from the language of the Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

, from the standard Serer-Sine  word "gari ñam" meaning "to eat", from the Serer
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

 Kingdom of Sine
Kingdom of Sine
The Kingdom of Sine was a pre-colonial Serer kingdom along the north bank of the Saloum River delta in modern Senegal. Much of the kingdom's population was and still is Serer.-History:...

. The Wolof people
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

 who have immigrated to another Serer Kingdom called the Kingdom of Saloum picked it up from the Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

 of Saloum
Saloum
The Kingdom of Saloum in Senegal is a traditional kingdom which was renamed Saloum in the late 15th century by the son of a Serer and a Guelowar from the kingdom of Kaabu to the south. The ancient and present capital of the Kingdom of Saloum is the city of Kahone. Previous to that, it was known...

 (the indigenous people). In Serer Saloum, the word is "ñaam" (nyam) which means "to eat". Whilst in Serer-Sine (proper Serer) it is "gari ñam" (gari nyam) meaning "to eat", in Saloum
Saloum
The Kingdom of Saloum in Senegal is a traditional kingdom which was renamed Saloum in the late 15th century by the son of a Serer and a Guelowar from the kingdom of Kaabu to the south. The ancient and present capital of the Kingdom of Saloum is the city of Kahone. Previous to that, it was known...

 it is merely shortened to "ñaam". The word derives from the proper Serer word "ñam" (nyam) which means "food". It is from that the Senegambian word "ñaambi" (cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

) originated from. These words are used by all Senegambians not just by the Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

 (the progenitors of these words), but also by the Wolof people
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

, the Fula people
Fula people
Fula people or Fulani or Fulbe are an ethnic group spread over many countries, predominantly in West Africa, but found also in Central Africa and Sudanese North Africa...

, the Mandinka people
Mandinka people
The Mandinka, Malinke are one of the largest ethnic groups in West Africa with an estimated population of eleven million ....

 etc.
The Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

 also being ancestors of the Wolof people
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

 as they are the ancestors of the Toucouleur people and Lebou people, their language has also been borrowed and diluted by these groups. "Cheikh Anta Diop
Cheikh Anta Diop
Cheikh Anta Diop was a historian, anthropologist, physicist, and politician who studied the human race's origins and pre-colonial African culture. He is regarded as an important figure in the development of the Afrocentric viewpoint, in particular for his theory that the ancient Egyptians were...

 had defended the hypothesis that the Wollofs
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

 were not originally a group apart but the result of a process of metissage so to speak of different ethnic groups: Serere
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

, Lebou, Toucoulor, Mandinka
Mandinka people
The Mandinka, Malinke are one of the largest ethnic groups in West Africa with an estimated population of eleven million ....

 and Sarahuli who, in their evolution i.e. the Wollofs
Wolof people
The Wolof are an ethnic group found in Senegal, The Gambia, and Mauritania.In Senegal, the Wolof form an ethnic plurality with about 43.3% of the population are Wolofs...

, transformed themselves into an autonomous "tribe" with a strong capacity to assimilate, absorb or integrate with all other ethnic groups. The Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

 also have an ancient tradition of farming not just millet
Millet
The millets are a group of small-seeded species of cereal crops or grains, widely grown around the world for food and fodder. They do not form a taxonomic group, but rather a functional or agronomic one. Their essential similarities are that they are small-seeded grasses grown in difficult...

 and other crops but cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...

 ("ñaambi") as well. The Europeans who came to Africa especially the Portuguese who were the first Europeans to arrive in Senegambia may have picked it up from the Serer people
Serer people
The Serer people along with the Jola people are acknowledged to be the oldest inhabitants of The Senegambia....

.
The Fula nomad
Nomad
Nomadic people , commonly known as itinerants in modern-day contexts, are communities of people who move from one place to another, rather than settling permanently in one location. There are an estimated 30-40 million nomads in the world. Many cultures have traditionally been nomadic, but...

 who have travelled to other parts of West Africa e.g. Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

 etc, would have also adopted these Serer words and spread it among the population. In West Africa, there is a mutual exchange when it comes to food, for example "Jolof Rice" which is in reference to the Kingdom of Jolof in modern day Senegal, has spread to Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

 and Ghana
Ghana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...

. In similarity, the Nigerian food "Akara" has spread to both Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...

 and The Gambia
The Gambia
The Republic of The Gambia, commonly referred to as The Gambia, or Gambia , is a country in West Africa. Gambia is the smallest country on mainland Africa, surrounded by Senegal except for a short coastline on the Atlantic Ocean in the west....

.

There are over 100 ethnic groups and languages in Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

, and each has different language names for Yam, "Isu" is the Yoruba translation or "Iyan" when it has been prepared to be consumed as a main course for dinner.

Other uses of the term yam

Several other unrelated root vegetables are sometimes referred to as "yams", including:
  • In the United States
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

    , sweet potato
    Sweet potato
    The sweet potato is a dicotyledonous plant that belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. Of the approximately 50 genera and more than 1,000 species of...

     (Ipomoea
    Ipomoea
    Ipomoea is the largest genus in the flowering plant family Convolvulaceae, with over 500 species. Most of these are called "morning glories", but this can refer to related genera also. Those formerly separated in Calonyction are called "moonflowers"...

     batatas
    ), especially those with orange flesh, are often referred to as "yams." In the United States, firm varieties of sweet potatoes were produced before soft varieties. When soft varieties were first grown commercially, there was a need to differentiate between the two. African slaves had already been calling the soft sweet potatoes "yams" because they resembled the yams in Africa. Thus, soft sweet potatoes were referred to as yams to distinguish them from the firm varieties. Sweet potatoes labeled as "yams" are widely available in markets that serve Asian or Caribbean communities. Today the U.S. Department of Agriculture requires sweet potatoes labeled with the term "yam" to be accompanied by the term "sweet potato."

  • In New Zealand
    New Zealand
    New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

     "yam" refers to the oca
    Oca
    Oxalis tuberosa is an herbaceous perennial plant that overwinters as underground stem tubers. These tubers are known as oca, oka, or New Zealand Yam. The plant was brought into cultivation in the central and southern Andes for its tubers, which are used as a root vegetable...

     (Oxalis tuberosa).

  • The corm
    Corm
    A corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat ....

     of the konjac
    Konjac
    Konjac , also known as konjak, konjaku, konnyaku potato, devil's tongue, voodoo lily, snake palm, or elephant yam , is a plant of the genus Amorphophallus...

     is often colloquially referred to as a yam, although it is unrelated.

  • In Malaysia and Singapore
    Singapore
    Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

    , "yam" is used to refer to taro
    Taro
    Taro is a common name for the corms and tubers of several plants in the family Araceae . Of these, Colocasia esculenta is the most widely cultivated, and is the subject of this article. More specifically, this article describes the 'dasheen' form of taro; another variety is called eddoe.Taro is...

    .

See also

  • Diosgenin
    Diosgenin
    Diosgenin, a steroid sapogenin, is the product of hydrolysis by acids, strong bases, or enzymes of saponins, extracted from the tubers of Dioscorea wild yam, such as the Kokoro...

     - A precursor to many steroids (derived from yam species, notably Dioscorea villosa and Dioscorea composita
    Dioscorea composita
    Dioscorea composita is a medicinal herb used in Ayurveda . The herb belongs to the family Dioscoreaceae.The herb is native of Mexico and has been domesticated in several tropical countries including India....

    ).
  • Konjac
    Konjac
    Konjac , also known as konjak, konjaku, konnyaku potato, devil's tongue, voodoo lily, snake palm, or elephant yam , is a plant of the genus Amorphophallus...

     - a Japanese vegetable with similar uses.
  • Yam (disambiguation), for a variety of uses of the word yam.
  • Yam production in Nigeria
    Yam production in Nigeria
    Nigeria is by far the world’s largest producer of yams, accounting for over 70–76 percent of the world production. According to the Food and Agricultural Organization report, in 1985, Nigeria produced 18.3 million tonnes of yam from 1.5 million hectares, representing 73.8 percent of total yam...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK