Sweet Potato

Ipomoea batatas (L.) Lam.

Sweet Potato myfavouritepastime.com

Family: Convolvulaceae (Morning Glory Family) Also known as Kumara (Maori), Patate douce (Fr)

Sweet potato is a native of tropical regions in America. It was carried to Europe by Columbus and to Asia by other explorers. There are over 1000 species in the family convolvulaceae but sweet potato is the only crop plant of major importance.

The sweet potato is not related to the “Irish Potato” (regular potato used for making French fries). The regular potato is called Solanum tuberosum and is closely related to tomato and eggplant. Regular potato is a tuberous stem and the sweet potato is a tuberous root, like carrot and other tuberous roots like radish and cassava.

Sweet Potato myfavouritepastime.com

Production

Sweet potato is cultivated throughout tropical and warm temperate regions with sufficient water to support it’s growth. Major producers in order of importance are: China followed by Uganda, Nigeria,, Indonesia, Tanzania, Vietnam, India and USA. Propagation: is by stem or root cutting or adventitious roots called “slips” that grow our from the tuberous root during storage.

The Sweet Potato Tuber

The sweet potato is a large, starchy and nutritious tuberous root with an intense natural sweetness which is produced by an enzyme that converts most of the starches to sugars as the potato matures. The sweetness continues to increase during storage and during cooking.

The tuberous roots are usually long and tapered but may be variously shaped depending on the cultivar. The skin is smooth and the colour ranges from yellow, orange, red, brown, purple and beige. The flesh ranges from beige to white, red, pink, violet, yellow, orange and purple. The orange fleshed sweet potato has more beta carotene, a precursor of vitamin A, so it’s being promoted in Africa and parts of Asia, as an important way to prevent vitamin A deficiency.

Dry or Moist Sweet potatoes?

In general sweet potatoes can be dry and floury with a fluffier consistency and a more delicate flavour or they can be soft and moist. The moist orange fleshed cultivars dominate the N. American market but you can find dry, yellow ones too.

Should Sweet Potatoes be called yam?

In North America, especially the USA, soft, moist, orange, sweet potatoes are often erroneously called “Yams“. Please note that the true yams, come from the Genus Dioscorea (family Dioscoraceae) and are a native to Africa and Asia. They are usually much larger, longer and cylindrical, with a white flesh. True yams do not occur in America.
How to differentiate between sweet potato and yam

Curing of Sweet Potato

If you plan to use up the sweet potato harvest within a month or two, it isn’t necessary to “cure” them. Simply air-dry the tubers for 7 to 10 days at 75 to 80º F. (24-27ºC). However cured potatoes tend to be sweeter.

Sweet potatoes are traditionally cured to improve storage period, flavour and nutrition. Dry freshly dug roots are dried on the ground for 2-3 hours then cured at 29-32C (85-90F) and 85-90% relative humidity for 4-7 days. Cured sweet potatoes can keep for up to 12 months at 13-15C (55-59F) and 85-90% relative humidity.

Nutrition

100g (3.5oz) Raw Sweet Potato: 20% starch, 4.2% sugar, Vitamin A equiv. 89%, beta carotene (79%), Vitamin C  (3%), manganese (12%) and B6 (16%). Provitamin A carotenoid.

100g (3.5oz) BAKED IN SKIN: 20.7% carbohydrate; energy 90kcal; sugars, 6.5%; vitamin A equiv. 120%, Manganese (24%); Vitamin C (24%) B6 (22%). There is an increase of several nutrients after cooking..

Use of Sweet Potato

  1. Several countries use sweet potato as staple food: Papua New Guinea, (500kg) per person per year, Solomon Islands, Burundi, Rwanda, and Uganda.
  2. Sweet potatoes can be eaten raw, or cooked; boiled, steamed, mashed, fried, or baked.
  3. They are eaten as a snack, dessert, main dish or side dish.
  4. Sweet potatoes are also sold canned or frozen.
  5. Dried tubers can be milled into flour and used in baking bread, biscuits, cakes and doughnuts.
  6. The young leaves and vine tips of sweet potatoes are edible and provide an important source of food in Africa and Asia.
  7. Half of the Chinese crop of sweet potato is used for livestock. Growers cure them before making the feed. (please confirm)
  8. Leafy shoots are also used as a feed for livestock at milking time.
  9. Less sweet cultivars are bred for industrial production of starch.
  10. ORNAMENTAL: some cultivars of Ipomoea batatas are grown as ornamental plants and are referred to as tuberous morning glory.

Storage of Sweet Potatoes

  1. Sweet potatoes are subject to rapid spoilage if not stored properly. Handle fresh potatoes with care because their skins are quite thin and are easily damaged. Cured potatoes, sold at the grocery store, have a thicker skin.
  2. Don’t wash potatoes until you’re ready to cook them as moisture will hasten spoilage.
  3. Store sweet potatoes at 12-15°C (55-60°F) in a dry place such as pantry or cellar for more than one month. If stored at room temperature, (23-25.5°C; 73-78°F), they should be used within a week.
  4. Don’t store sweet potatoes in the fridge because they may develop a hard core and an off taste.
  5. Cooked, sliced or mashed sweet potatoes, can be frozen. Add a little lemon juice to keep them from darkening. Pack into freezer containers.

References

  1. Wikipedia on Sweet Potato 
  2. Harvesting, Curing and Storage of Sweet Potatoes
  3. Some varieties of sweet potato

 

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