Sweet potato

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For the musical instrument, see ocarina.

The sweet potato (Ipomoea batatas) is a crop plant whose large, starchy, sweet tasting tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). Although sweet potatoes are sometimes called "yams" in the United States, they are even more distantly related to the true yam (Dioscorea species).

The genus Ipomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. Some cultivars of Ipomoea batatas are grown as houseplants.

The plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between red, purple, brown and white. Its flesh ranges between white, yellow, orange, and purple.

Origin and distribution

Sweet potatoes are native to the tropical Americas and were domesticated there at least 5000 years ago. [1] [2] They spread very early throughout the region, including the Caribbean. They were also known before western exploration in Polynesia. How exactly they arrived there is the subject of a fierce debate which involves archaeological, linguistic and genetic evidence.

Sweet potatoes are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.

According to 2004 FAO statistics world production is 127,000,000 tons [3]. The majority comes from China with a production of 105,000,000 tonnes from 49,000 km². About half of the Chinese crop is used for livestock feed [4].

Per-capita production is greatest in countries where sweet potatoes are a staple of human consumption, led by the Solomon Islands at 160 kg per person per year and Burundi at 130 kg.

North Carolina is the leading U.S. state in sweet potato production. Currently, North Carolina provides 40% of the annual U.S. production of sweet potatoes.

Mississippi is also a major sweet potato producing state. Sweet potatoes are produced on approximately 8200 acres in the state. Mississippi sweet potatoes contribute $19 million dollars to the economy of the state. Presently, approximately 150 Mississippi farmers grow sweet potatoes. Mississippi's top five sweet potato producing counties are Calhoun, Chickasaw, Pontotoc, Yalobusha and Panola. The National Sweet Potato Festival is held annually the entire first week in November in Vardaman, MS, which proclaims itself as "The Sweet Potato Capitol".

The town of Benton, Kentucky, celebrates the sweet potato annually with its Tater Day Festival on the first Monday of April.

Cultivation

The plant does not tolerate frost. It grows best at an average temperature of 24 °C (75 °F). Depending on the cultivar and conditions, tuberous roots mature in 2 to 9 months. With care, early-maturing cultivars can be grown as an annual summer crop in temperate areas, such as the northern USA. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are mostly propagated by stem or root cuttings or by adventitious roots called "slips" that grow out from the tuberous roots during storage. True seeds are used for breeding only.

Under optimal conditions of 85 to 90 % relative humidity at 13 to 16 °C (55 to 61 °F), sweet potatoes can keep for six months. Colder temperatures injure the roots.

Sweet potatoes are often considered a small farmer's crop. They grow well in many farming conditions and have few natural enemies, pesticides are rarely needed. They can be grown in poor soils with little fertilizer. Because they are sown by vine cuttings rather than seeds sweet potatoes are relatively easy to plant. Because the rapidly growing vines shade out weeds little weeding is needed, allowing farmers to devote time to other crops. In the tropics the crop can be maintained in the ground and harvested as needed for market or home consumption. In temperate regions sweet potatoes are most often grown on larger farms and are harvested before frosts set in.(CGIAR)

China is the largest grower of sweet potatoes; providing about 80% of the world's supply, which totaled 130 million tons in 1990 (about half that of common potatoes). In the past most of China's sweet potatoes were grown for food but now most (60%) are grown to feed pigs. The rest are grown for human food and for other products. Some are grown for export, mainly to Japan. China grows 100 varieties of sweet potato.(JRT)

Sweet potatoes very early became popular in the islands of the Pacific from Japan to Polynesia. One reason is that they were favored as an emergency crop which could be relied on if other crops failed, for instance because of typhoon flooding. They are featured in many favorite dishes in Japan, Taiwan, the Philippines , and other island nations. Indonesia, Vietnam, India, and some other Asian countries are also large sweet potato growers. Uganda (the third largest grower after Indonesia), Rwanda, and some other African countries also grow a large crop which is an important part of their peoples' diets. North and South America, the original home of the sweet potato, together grow less than three percent of the world's supply. Europe has only a very small sweet potato production, mostly in Portugal.(JRT)(FAO)

Sweet potatoes were an important part of the diet in the United States for most of its history, especially in the Southeast. In recent years however they have become less popular. The average per capita consumption of sweet potatoes in the United States is only about 1.5-2 kg (4 lbs) per year, down from 13 kg (31 lb) in 1920. Southerner Kent Wrench writes: "The SweetPotato became associated with hard times in the minds of our ancestors and when they became affluent enough to change their menu, the potato was served less often."(NCSPC)

Uses

Although the leaves and shoots are also edible, the starchy tuberous roots are by far the most important product. In some tropical areas, they are a staple food-crop. Besides starch, they are rich in dietary fiber, vitamin A, vitamin C, and vitamin B6. All cultivars are more-or-less sweet-flavored.

In 1992, the Center for Science in the Public Interest compared the nutritional value of sweet potatoes to other vegetables. Considering fiber content, complex carbohydrates, protein, vitamins A and C, iron, and calcium, the sweet potato ranked highest in nutritional value. According to these criteria, sweet potatoes earned 184 points, 100 points over the next on the list, the common potato.(NCSPC)

Sweet potato varieties with dark orange flesh have more Vitamin A than those with light colored flesh and their increased cultivation is being encouraged in Africa where Vitamin A deficiency is a serious health problem.

The roots are most frequently boiled, fried, or baked. They can also be processed to make starch and a partial flour substitute. Industrial uses include the production of starch and industrial alcohol.

Candied sweet potatoes are a side dish consisting mainly of sweet potatoes prepared with sugar, marshmallows, maple syrup, molasses, or other sweet ingredients. Often served on American Thanksgiving, it represents traditional American cooking and indigenous food. Some Americans, including television personality Oprah Winfrey, are presently advocating increased consumption of sweet potatoes both for their health benefits and because of their importance in traditional Southern cuisine.

Boiled sweet potato leaves are a common side dish in Taiwanese cuisine, often boiled with garlic and vegetable oil and dashed with salt before serving. They are commonly found at biàndāng restaurants, as well as dishes featuring the sweet potato root.

All parts of the plant are used for animal feed.

They can also be sliced, fried, and eaten just like potato chips.

In South America, the juice of red sweet potatoes is combined with lime juice to make a dye for cloth. By varying the proportions of the juices, every shade from pink to purple to black can be obtained.(Verrill p. 47)

In Japan, sweet potato is a key ingredient in the finest variety of shochu, imo-jochu, which is distilled from rice and sweet potato.

Ethnomedical Uses

• The aerial roots are used as a galactogogue.
• The leaves are used to treat diabetes hookworm, hemorrhage, and abscesses.
• The tuber is used to treat asthma.

Names

The moist-fleshed, orange cultivars of sweet potato are often referred to as “yams” in the United States. One explanation of this confusion is that Africans brought to America took to calling American sweet potatoes Nyamis, perhaps from the Fulani word nyami (to eat) or the Twi word anyinam, which refers to a true yam. The true yam, which is native to Africa and Asia, can grow up to 2 m (6 ft) in length (sometimes with knuckle-like ends) and has a scaly skin, a pinkish white center, and a thick, almost oily feel to the tongue.

Later on many farmers and stores began marketing American-grown sweet potatoes as yams; the name stuck. In more recent times there has been an effort to stop the use of “yam” for sweet potatoes, but this has only been partially successful. USDA branding regulations require the word “yam” to be accompanied by the words “sweet potato” when referring to these moister sweet potatoes.

Starchy, white-fleshed types are sometimes called batatas or boniatos, from dialectal Spanish terms which in Spanish refer generically to all types of sweet potato.

Substratum names used in local varieties of English include kumara (from Māori) in the UK and Australasia (the term is also used in indigenous languages of Melanesia, as well as "peteita"), and camote (from Nahuatl camohtli via Spanish) in the southwestern United States.

In Hawaiʻi substratum names are used for the yellow Japanese variety and the purple Okinawan variety, both of which are commonly available in the marketplace. The local Japanese names are widely recognized, with Satsumaimo “Satsuma potato” used by recent Japanese immigrant families and yamaimo (“mountain potato”, probably a corruption of amai imo “sweet potato”) by other groups. However, naming often depends on personal ancestry, with e.g. Sāmoan ʻumala among Sāmoans, Tagalog kamote among Filipinos, and Hawaiian ʻuala among Native Hawaiians. The orange-fleshed variety common in the mainland US and sold alongside the Japanese and Okinawan cultivars is locally called “sweet potato” or “yam”. The purple Okinawan sweet potato is sometimes confused with the purple yam called ube.

Varieties

There are seven major varieties of sweet potatoes: Jersey, Kotobuki (Japanese), Okinawan (Purple), Papa Doc, Beauregard, Garnet, and Jewel. The last three varieties are regionally called "yams" in the United States.

References and external links

• Batatas, not potatoes
• The mystery of the sweet potato
• Sweet Potato Growing and Harvesting Information
• The Hall of Ma'at
• Sweet potatoes gathering in the rainforest
• Purple sweetpotato Exotic sweetpotatoes can have purple flesh.
• Six Varieties of Sweet Potatoes Explanation of the six major varieties of sweet potatoes, with pictures of the exterior and interiors of four varieties.
• Fortified Sweet Potato Helps Fight Malnutrition
• Consultative Group on International Agricultural Research (CGIAR), "Sweet Potato"[5]
• Food and Agricultural Organization of the United Nations (FAO), 1990, "Roots, tubers, plantains and bananas in human nutrition" [6]
• The Japanese Society of Root and Tuber Crops (JRT), "Mini White Paper: Sweetpotato in Japan" 2000 [7]
• North Carolina Sweet Potato Commission (NCSPC) Website.[8]
• Verrill, A.H., Foods America Gave the World, 1937, Boston : L.C. Page & Co.
• Wrench, K., "The Sweet Potato Patch"[9]
• National Sweet Potato Month
• [10] Sweet potato recipes
• [11] Sweetpotato DiagNotes is a free comprehensive tool for sweetpotato management, providing information across the disciplines of plant pathology, crop nutrition, entomology and pest management, all integrated in a single expert system.