Sweet corn

Husked sweetcorn, Corn on the cob

Sweet corn (Zea mays var. rugosa), also called indian corn, sweetcorn (the only term usual in UK English), 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 (dent stage), sweet corn is picked when immature (milk stage) 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 fresh, canned, or frozen before the kernels become tough and starchy.

Sweetcorn (seeds only)

Nutritional value per 100 g (3.5 oz)
Energy	360 kJ (86 kcal)
Carbohydrates	19 g
Sugars	3.2 g
Dietary fiber	2.7 g
Fat	1.2 g
Protein	3.2 g
Vitamins and minerals Vitamins Quantity %DV† Vitamin A equiv. 1% 10 μg Folate (B9) 12% 46 μg Vitamin C 8% 7 mg Minerals Quantity %DV† Iron 3% 0.5 mg Magnesium 9% 37 mg Potassium 9% 270 mg
†Percentages estimated using US recommendations for adults, except for potassium, which is estimated based on expert recommendation from the National Academies.

History

Young sweet corn

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. It soon became a popular vegetable in southern and central regions of the United States.

Open pollinated varieties of white sweet corn started to become widely available in the United States in the 19th century. Two of the most enduring varieties, still available today, are Country Gentleman (a Shoepeg corn with small, white kernels in irregular rows) and Stowell's Evergreen.

Sweet corn production in the 20th century was influenced by the following key developments:

• hybridization allowed for more uniform maturity, improved quality and disease resistance
• identification of the separate gene mutations responsible for sweetness in corn and the ability to breed varieties based on these characteristics:
  • su (normal sugary)
  • se (sugary enhanced, originally called Everlasting Heritage)
  • sh2 (shrunken-2)

There are currently hundreds of varieties, with more constantly being developed.

Anatomy

The same rows of corn 41 days later at maturity.

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. Because corn is a monocot, there is always an even number of rows of kernels. 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

In Latin America, sweet corn is traditionally eaten with beans; each plant is deficient in an essential amino acid that happens to be abundant in the other, so together sweet corn and beans form a balanced diet in the absence of meat. Similarly, sweet corn in Latin America is traditionally ground or soaked with limestone, which makes available a B vitamin in the corn, the absence of which would otherwise lead to a deficiency disease.

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. Corn on the cob 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 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.

Health benefits

Sweet corn on the cob

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."

Varieties

Main article: List of sweetcorn varieties

File:Truckbed of Corn.jpg

Sweet corn that has not been husked yet, headed to market.

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. Su varieties are best when cooked within 30 minutes of harvest. 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 three known genetic mutations responsible for the various types of sweet corn. Early varieties, such as those used by Native Americans, were the result of the mutant su ("sugary") allele. They contain about 5-10% sugar by weight.

Supersweet corn are varieties of sweet corn which produce higher than normal levels of sugar. 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 su sweet corn. He published his findings in 1953, disclosing the advantages of growing supersweet sweet corn, but many corn breeders lacked enthusiasm for the new supersweet corn. Illinois Foundation Seeds Inc. was the first seed company to release a supersweet corn and it was called Illini Xtra Sweet, but widespread use of supersweet hybrids did not occur until the early 1980's. The popularly of supersweet corn rose 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.

Cut Sweet White Corn

The third gene mutation to be discovered is the se or "sugary enhanced" allele, responsible for so-called "Everlasting Heritage" varieties, such as Kandy Korn. Varieties with the se alleles have a longer storage life and contain 12-20% sugar compared to su varieties.

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).

Modern breeding methods have also introduced varieties incorporating multiple gene types:

• sy (for synergistic) adds the sh2 gene to some kernels (usually 25%) on the same cob as a se base (either homozygous or heterozygous)
• augmented sh2 adds the se and su gene to a sh2 parent

Often seed producers of the sy and augmented sh2 types will use brand names or trademarks to distinguish these varieties instead of mentioning the genetics behind them.

Bt corn

Bt corn resists certain insects and commercial growers have access to sweet corn seed bred with this artificial trait. Bt corn and other transgenic varieties are not available to the home grower due protocols that must be followed in their production.

Growing sweet corn

Soil pH: 6pH to 6.5pH Sun: Full Sun Tilling Depth: 10 inches Planting Depth: 1 inch deep Planting pattern: Use a block pattern, 3 to 4 short rows side by side Fertilize: 12" in height, for tall varieties, 18" - 24" high Harvest: 64 days Seedlings emerge: 7-14 days

Choosing varieties

For the beginner who only has space for one variety, Early Sunglow is a good choice. If you have space for two blocks of corn, go with Early Sunglow and Golden Cross Bantam, or just make a second planting of Early Sunglow 15 to 30 days after the first. These varieties are among the hardiest and easiest to grow, and seed racks in local department or hardware stores are likely to have them. Once you have successfully grown corn, in future years try other varieties in the se, sh2 and sy types. These may need to be planted a couple weeks later for sufficient warmth and have somewhat lower germination rates. Don't be afraid to try white and bicolor too. Just be sure to isolate supersweet varieties (sh2 or augmented sh2) from other corn by either more than 100 ft(33 m) or more than 15 days in maturity time.

See also

• List of sweetcorn varieties
• Cornbread
• Cornmeal
• Creamed corn
• Frozen vegetables