(Ipomoea batatas – Family Convolvulaceae)
Sweet Potato, Kumara, Louisiana Yam, Yellow Yam
Often called a yam, the sweet potato is a member of the Morning Glory family (Convolvulaceae) and not the Yam family (Dioscoreaceae), but that is only the beginning of the confusion.
The first Europeans to taste sweet potatoes were members of Columbus’ expedition to Haiti in 1492. Later explorers found many varieties under an assortment of local names, but the name which stayed was the Haitian name of batata. This name was later transferred to the ordinary potato, causing a confusion from which it never recovered.
The first record of the name sweet potato is found in the Oxford English Dictionary of 1775. Kumara is the Polynesian name for an orangey-fleshed vegetable that looks like a sweet potato, and is a tuberous relative of the morning glory (sweet potato). It has a rich nutty taste that works well with other vegetables in stir fry.
The sweet potato is the cultivated descendant of a wild plant whose tuberous remains have been found in a cave in Peru which was inhabited before 8000 BCE. It was cultivated during the last centuries of BCE and well before the time of the Inca.
It was a staple food all over tropical America as far north as Mexico, as well as on the Caribbean islands. It is likely that, during the 13th century, the sweet potato made its way to the Easter Islands and Hawaii, and then on to New Zealand in the next century. These dates have been taken from both Hawaiian and Maori records.
Before the Kon-Tiki expedition in 1947, when Thor Heyerdahl proved that voyages across the ocean were deliberate ventures and not out of the realm of possibility, it had been thought that the sweet potato must have been carried to the Pacific Islands by Europeans at a much later date.
With Heyerdahl’s demonstration came the support for the fact that the ancient Peruvian name for the tuber, kumar, is found with only minor variations (kumala, gumala, umala) in several of the Pacific island languages.
Sixteenth century Spanish explorers took the sweet potato to the Philippines; and, from there, Portuguese traders spread it throughout the East Indies and India.
By the end of that century, it had made its way into China, where a famine in Fujian province in 1593 caused the governor to send out an expedition to the Philippines in search of food plants. The following year, the ships returned with the sweet potato, which soon became a staple food in China; but it was not until the 18th century that the sweet potato made its way into Japan.
The Japanese names indicate its route of travel from China to Okinawa. Polynesia began cultivating it before 1250, and New Zealand, by the 14th century. Captain Cook and Sir Joseph Banks found the Maoris of the North Island growing it when they landed in 1769.
In North America, sweet potatoes have long been grown by the Indians in Louisiana, where de Soto found them in 1540, and also farther north in Georgia. By 1648, colonists in Virginia were cultivating them.
They were especially valued during the war against the British and the Civil War as it grew quickly underground and, therefore, less vulnerable to destruction than surface crops.
It was likely slave traders who introduced it to Africa; and, ever since, it has been slowing replacing the true yam as a major carbohydrate food in the tropical African diet.
It reached England via the Canary Islands and was the common potato during the Elizabethan years. At that time, sweet potatoes were sold in crystallized slices with sea holly (eringo) as an aphrodisiac.
This was portrayed in such plays as “The Merry Wives of Windsor” (“Let the sky rain potatoes…hail kissing comforts and snow eringoes”).
The Empress Josephine introduced sweet potatoes to her companions, who were soon serving them to stimulate the passion of their lovers. But alas, those results are not recorded!
The sweet potato ranks fifth on the world’s list of most important food staples after rice, wheat, corn, and cassava, as it constitutes a substantial source of carbohydrate and carotene.
More than 90% of the world’s sweet potatoes are grown in Asia, and most are not orange-fleshed.
The moist, orangey ones are grown mainly in the US and Australia. Such orange-fleshed ones as Beauregard, the primary commercial type, and the smaller Jewel and Garnet, are the main ones grown for North American markets. They are sweet and moist but do have a pumpkiny flavour to them.
The sweet potatoes preferred outside the US and Canada are white-fleshed
and not usually soft or sweet; but they are more versatile than the orange types, fitting into meals like the common potato.
Oriental type sweet potatoes
are those with various Asian names that the market uses for rose-skinned, ivory-fleshed cultivars developed in the Far East.
They fall between the drier boniato types and the moist-fleshed whites.
Boniato types are burly, dented, dark red-coloured tubers that are well represented throughout Latin and Far Eastern markets. Boniato is often regarded as a vegetable in its own right, although it is correctly a cultivar of the sweet potato. It came to the US by way of Cuba and the Antilles, and has remained popular ever since.
Sweet potatoes are usually not eaten raw but we do so.
Baking them is the preferred method by most people as most of the nutrients are found just under the skin; although organically grown sweet potatoes can be eaten raw with the skins on and grated into a salad, for instance.
Sweet potatoes are high in vitamins A, C, and E, as well as B6, folate, potassium, and iron. The deeper colour of the flesh indicates a higher content of carotene.
However, sweet potatoes provide only half as much protein as ordinary potatoes, but less starch and sugar. The tubers do not store well, however.
The Maori dry the whole root, while the Chinese slice and sun-dry their tubers. Other countries may candy them. Sweet potato or Yam fries are also becoming more popular.
Sweet potatoes and their leaves contain antibacterial and antifungal substances that have long been used in folk medicines.
There are hundreds of sweet potato varieties worldwide. Most are elongated and slightly pointed, although some may be round.
The skin may be white, yellow, red, purple, or brown; with the flesh being white, yellow, orange, or orange-red.
The two main categories are soft and firm, indicating how they turn out after cooking. The flesh of the soft ones are more likely to be orange, while the firm ones are white or yellow.
In the US, the soft kinds are sometimes called “yams”. The most remarkable variety (Ipomoea leptophylla) is the manroot (man of the earth), which grows in the western US and can literally be the size and shape of a full-grown man. It is not very good to eat and most difficult to dig up so it is usually relegated for use as a famine food.
Sweet potatoes are classified as three types: dry and mealy fleshed, soft and moist fleshed, and coarse fleshed used as animal feed.
White or pale types make good flour, having a chestnut-caramel flavour.
Yellow and orange varieties are sweet and watery.
Some varieties are as follows:
Centennial has bright copper-orange skin and deep orange flesh.
Jewel has copper-coloured tubers with moist white flesh.
Porto Rico Bush has deep orange sweet flesh, and is excellent for baking.
Tokatoka Gold is large, rounded and smooth textured. It is popular in New Zealand.
Vardaman does not vine, but it does produce golden-yellow skinned tubers with deep red-orange flesh.
