20 Feb 2014

Sweet Potato

*SWEET POTATO*

(Peru)


Orange-fleshed sweet potatoes may be one of nature's unsurpassed sources of beta-carotene. Several recent studies have shown the superior ability of sweet potatoes to 
raise our blood levels of vitamin A. This benefit may be particularly true for children. In several studies from Africa, sweet potatoes were found to contain between 100-1,600 
micrograms (RAE) of vitamin A in every 3.5 ounces—enough, on average, to meet 35% of all vitamin A needs, and in many cases enough to meet over 90% of vitamin A 
needs (from this single food alone). Sweet potatoes are not always orange-fleshed on the inside but can also be a spectacular purple color. Sometimes it's impossible to tell 
from the skin of sweet potato just how rich in purple tones its inside will be. That's because scientists have now identified the exact genes in sweet potatoes (IbMYB1 and 
IbMYB2) that get activated to produce the purple anthocyanin pigments responsible for the rich purple tones of the flesh. The purple-fleshed sweet potato 
anthocyanins primarily peonidins and cyanidins have important antioxidant properties and anti-inflammatory properties. Particularly when passing through our digestive 
tract, they may be able to lower the potential health risk posed by heavy metals and oxygen radicals. The sweet potato (Ipomoea batatas) is a dicotyledonous plant that 
belongs to the family Convolvulaceae. Its large, starchy, sweet-tasting, tuberous roots are a root vegetable. The young leaves and shoots are sometimes eaten as greens. Of 
the approximately 50 genera and more than 1,000 species of Convolvulaceae, I. batatas is the only crop plant of major importance some others are used locally, but many 
are actually poisonous. The sweet potato is only distantly related to the potato (Solanum tuberosum) and does not belong to the nightshade family. 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 yellow, orange, red, brown, purple, and beige. Its flesh ranges from beige through white, red, pink, violet, yellow, orange, and 
purple. Sweet potato varieties with white or pale yellow flesh are less sweet and moist than those with red, pink or orange flesh. The center of origin and domestication of 
sweet potato is thought to be either in Central America or South America. In Central America, sweet potatoes were domesticated at least 5,000 years ago. In South 
America, Peruvian sweet potato remnants dating as far back as 8000 BC have been found. Austin (1988) postulated that the center of origin of I. batatas was between the 
Yucat√°n Peninsula of Mexico and the mouth of the Orinoco River in Venezuela. The 'cultigen' had most likely been spread by local people to the Caribbean and South 
America by 2500 BC. Zhang et al. (1998) provided strong supporting evidence that the geographical zone postulated by Austin is the primary center of diversity. 


The much 
lower molecular diversity found in Peru–Ecuador suggests this region should be considered as secondary center of sweet potato diversity. Besides simple starches, raw 
sweet potatoes are rich in complex carbohydrates, dietary fiber and beta-carotene (a provitamin A carotenoid), while having moderate contents of other micronutrients, 
including vitamin B5, vitamin B6, manganese and potassium (right table). When cooked by baking, small variable changes in micronutrient content occur to include a higher 
content of vitamin C at 24% of the Daily Value per 100 g serving (right table), as well as an increase in polyphenol levels. The Center for Science in the Public Interest has 
compared the nutritional value of sweet potatoes to other foods. Considering fiber content, complex carbohydrates, protein, vitamin A and potassium, the sweet potato 
ranked highest in nutritional value. Sweet potato varieties with dark orange flesh have more beta carotene than those with light-colored flesh, and their increased cultivation is 
being encouraged in Africa, where vitamin A deficiency is a serious health problem. A 2012 study of 10,000 households in Uganda found that 50% of children who ate normal 
sweet potatoes suffered from vitamin A deficiency compared with only 10% of those on the high beta carotene variety.  Sweet potatoes have a creamy texture and a 
sweet-spicy flavour that makes them ideal for savoury dishes. There are two types, one with bright orange flesh, the other with pale cream flesh. Sweet potatoes are native to 
the tropical Americas and are sometimes referred to as 'yams' in the USA. These tubers are rich in fibre, vitamins A, C and B6, and an excellent source of carbohydrates. 
The orange-fleshed variety are also rich in betacarotene. Sweet potatoes have traditionally been baked, roasted or mashed, but they can also be added to risotto, pasta or 
curry.


Try to choose small to medium-sized sweet potatoes with unblemished skins, as they will be more tender when cooked. Unless your sweet potatoes are particularly small 
and smooth, remove the skins with a peeler as they are often well-travelled and can be tough.


*If you will some recipes, please visit my blog
www.recipiesofcelia.blogspot.com

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