Sweet corn (Zea mays var. rugosa[1]), also called sweetcorn, sugar 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) | ||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Energy 90 kcal 360 kJ | ||||||||||||||||||||
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| Percentages are relative to US recommendations for adults. Source: USDA Nutrient database | ||||||||||||||||||||
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 cobb. 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. Corn on the cob is 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 cob 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.
Varieties
 | It has been suggested that Super sweet corn be merged into this article or section. (Discuss) |
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.
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.[4] 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.[5] 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).[6]
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
Eating cooked sweet corn significantly boosts the grain's health-giving 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 researchers found cooked sweet corn increases levels of antioxidants. 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.[7]
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.
- ^ "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
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