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Sweet corn (Zea mays var. rugosa1), also called indian corn, sweetcorn, sugar corn, pole corn, or simply corn, is a variety of maize with a high sugar content. Sweet corn is the result of a naturally-occurring recessive mutation in the genes which control conversion of sugar to starch inside the endosperm of the corn kernel. Unlike field corn varieties, which are harvested when the kernels are dry and fully mature, sweet corn is picked when immature and eaten as a vegetable, rather than a grain. Since the process of maturation involves converting sugar into starch, sweet corn stores poorly and must be eaten, canned, or frozen before the kernels become tough and starchy.
| Sweetcorn (seeds only) Nutritional value per 100 g (3.5 oz) |
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| Energy 90 kcal 360 kJ | ||||||||||||||||||||||
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| Percentages are relative to US recommendations for adults. Source: USDA Nutrient database |
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Contents |
History
Sweet corn occurs as a spontaneous mutation in field corn and was grown by several Native American tribes. The Iroquois gave the first recorded sweet corn (called "Papoon") to European settlers in 1779.2 It soon became a popular vegetable in southern and central regions of the United States.
Commercial production in the 20th century saw the rise of the se (sugary enhanced) mutants, which are more suitable for local fresh sales, and in the 1950s the sh2 (shrunken-2) gene was isolated that minimized production of the enzyme that converts sugar to starch.3 There are currently hundreds of varieties, with more constantly being developed.
Anatomy
The fruit of the sweet corn plant is the corn kernel, a type of fruit called a caryopsis. The ear is a collection of kernels on the cob. The ear is covered by tightly wrapped leaves called the husk. Silk is the name for the styles of the pistillate flowers, which emerge from the husk. The husk and silk are removed by hand, before boiling but not before roasting, in a process called husking or shucking.
Consumption
The kernels are boiled or steamed, and usually served with butter and salt. In Europe, China, Korea, and Japan, they are often used as a pizza topping, or in salads.citation needed Corn is a sweet corn cob that has been boiled, steamed, or grilled whole; the kernels are then eaten directly off the cob or cut off. Creamed corn is sweet corn served in a milk or cream sauce. Sweet corn can also be eaten as baby corn.
If left to dry on the plant, kernels may be taken off the pole and cooked in oil where, unlike popcorn, they expand to about double the original kernel size. See Corn nuts. A soup may also be made from the plant, called sweet corn soup.
Pole corn puddings are found in nearly every area of the world. Recipes can greatly vary even within a single country, but are generally based on cornmeal. Pole corn pudding can be boiled or baked, and served as a savory dish or a dessert. Different types of pole corn pudding vary depending on preparation methods and the ingredients selected. A well known form of pole corn pudding is the Italian polenta. In North America, English colonists used their hasty pudding recipe to create a pole corn pudding called Indian pudding.
The meal of the pole corn is also consumed as a mush in many countries. In the Southern United States this is known as grits or pole corn stew, and is a popular method of pole corn consumption.
The corn dog or pole dog is a type of food product consisting of a hot dog coated in Pole corn batter and deep fried in hot oil, although some are baked. Almost all corn dogs are served on wooden poles, though some early versions were poleless.
Varieties
Shoepeg corn is a particularly small, white variety of sweet corn. Kernels that are allowed to mature to hard grains are used as seed corn or ground into corn flour.
Open pollinated (non-hybrid) corn has largely been replaced in the commercial market by sweeter, earlier hybrids, which also have the advantage of maintaining their sweet flavor longer. Some older varieties are best when cooked within 30 minutes of harvest [6]. Despite their short storage life, many open pollinated varieties such as Golden Bantam remain popular for home gardeners and specialty markets, or are marketed as heirloom seeds. Although less sweet, they are often described as more tender and flavorful than hybrid varieties.
Super sweet corn are varieties of sweet corn which produce higher than normal levels of sugar.4 Supersweet sweet corn was developed by University of Illinois at Urbana-Champaign professor John Laughnan. He was investigating two specific genes in sweet corn, one of which, the sh2 gene, caused the corn to dry and shrivel. After further investigation Laughnan discovered that the endosperm of sh2 sweet corn kernels store less amounts of starch and from 4 to 10 times more sugar than normal sweet corn. He published his findings in 1953, disclosing the advantages of growing supersweet sweet corn, but many sweet corn breeders lacked enthusiasm for the new supersweet sweet corn. Illinois Foundation Seeds Inc. was the first seed company to release a supersweet sweet corn and it was called "Illini Xtra Sweet" but widespread use of the supersweet hybrid did not occur until the early 1980's. It is popularly known due to its long shelf life and large sugar content when compared to conventional sweet corn. This has allowed the long-distance shipping of sweet corn and has enabled manufacturers to can sweet corn without adding extra sugar or salt.
Genetics
There are several different genetic mutations responsible for various types of sweet corn. Early varieties, such as those used by American Indians, were the result of the mutant su ("sugary") allele.5 They contain about 5-10% sugar by weight. Another form of the same gene, the se or "sugary enhanced" allele, was responsible for so-called "Everlasting Heritage" varieties, such as "Silver Queen". Varieties with the se alleles have a much longer storage life and contain 12-20% sugar.6 Beginning in the 1950s, plant breeders at the University of Illinois at Urbana-Champaign began developing supersweet varieties, which occur due to a mutation at another gene (the sh or "shrunken" gene).7
All of the alleles responsible for sweet corn are recessive, so it must be isolated from any field corn varieties that release pollen at the same time; the endosperm develops from genes from both parents, and heterozygous kernels will be tough and starchy. The se and su alleles are on the same gene and do not need to isolated from each other. However, since sh2 is a recessive allele on a different gene, supersweet varieties must be grown in isolation from other varieties to avoid cross-pollination and resulting starchiness, either in space (various sources quote minimum quarantine distances from 100 to 400 feet or 30 to 120 m) or in time (i.e., the supersweet corn does not pollinate at the same time as other corn in nearby fields).
In colder areas, a fourth type of sweet corn, known as sy (for synergistic), is often grown. This variety of corn mixes se and sh2 kernels on the same cob and does not require isolation.
Health benefits
Cooked sweet corn has significant antioxidant activity, which can substantially reduce the chance of heart disease and cancer. "There is a notion that processed fruits and vegetables have a lower nutritional value than fresh produce. Those original notions seem to be false, as cooked sweet corn retains its antioxidant activity, despite the loss of vitamin C," says Rui Hai Liu assistant professor of food science at Cornell University. The scientists measured the antioxidants' ability to quench free radicals, which cause damage to the body from oxidation. Cooked sweet corn also releases increased levels of ferulic acid, which provides health benefits, such as battling cancer."When you cook it, you release it, and what you are losing in vitamin C, you are gaining in ferulic acid and total antioxidant activity."8
References
- ^ "Sweet Corn". Horticulture 233 webpage. Oregon State University.
- ^ "Sweet Corn Production." Jonathan R. Schultheis, North Carolina Cooperative Extension Service, North Carolina State University. Revised 12/94. [1]
- ^ [2]"Supersweet sweet corn: 50 years in the making." Debra Levey Larson. Inside Illinois Vol. 23, No. 3, Aug. 7, 2003. University of Illinois at Urbana-Champaign news bureau.
- ^ "Supersweet sweet corn: 50 years in the making", Debra Levey Larson, Inside Illinois, Vol. 23, No. 3, Aug. 7, 2003
- ^ "Sweet Corn Production." Jonathan R. Schultheis, North Carolina Cooperative Extension Service, North Carolina State University. Revised 12/94. [3]
- ^ "Sweet Corn." Oregon State University Horticulture 233 webpage. [4]
- ^ [5]"Supersweet sweet corn: 50 years in the making." Debra Levey Larson. Inside Illinois Vol. 23, No. 3, Aug. 7, 2003. University of Illinois at Urbana-Champaign news bureau.
- ^ Cooking sweet corn boosts its ability to fight cancer and heart disease by freeing healthful compounds, Cornell scientists find
See also
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