Sweetcorn
Overview
Sweet 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 mature (dent stage), sweet corn is picked when immature (milk stage) and prepared and eaten as a vegetable
, rather than a grain
.
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
with a high sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
content. Sweet corn is the result of a naturally occurring recessive
Recessive
In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
in the genes which control conversion of sugar to starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
inside the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...
of the corn kernel. Unlike field corn
Field corn
Field corn is maize of varieties that are not, in the United States, grown primarily for consumption as human food in the form of fresh kernels. More than 98% of corn-growing land in the U.S...
varieties, which are harvested when the kernels are dry and mature (dent stage), sweet corn is picked when immature (milk stage) and prepared and eaten as a vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
, rather than a grain
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
.
Unanswered Questions
Encyclopedia
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
with a high sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
content. Sweet corn is the result of a naturally occurring recessive
Recessive
In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
in the genes which control conversion of sugar to starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
inside the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...
of the corn kernel. Unlike field corn
Field corn
Field corn is maize of varieties that are not, in the United States, grown primarily for consumption as human food in the form of fresh kernels. More than 98% of corn-growing land in the U.S...
varieties, which are harvested when the kernels are dry and mature (dent stage), sweet corn is picked when immature (milk stage) and prepared and eaten as a vegetable
Vegetable
The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....
, rather than a grain
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
. Since the process of maturation involves converting sugar to starch, sweet corn stores poorly and must be eaten fresh, canned
Canning
Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a typical shelf life ranging from one to five years, although under specific circumstances a freeze-dried canned product, such as canned, dried lentils, can last as...
, or frozen, before the kernels become tough and starchy.
History
Sweet corn occurs as a spontaneous mutation in field cornField corn
Field corn is maize of varieties that are not, in the United States, grown primarily for consumption as human food in the form of fresh kernels. More than 98% of corn-growing land in the U.S...
and was grown by several Native American
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
tribes. The Iroquois
Iroquois
The Iroquois , also known as the Haudenosaunee or the "People of the Longhouse", are an association of several tribes of indigenous people of North America...
gave the first recorded sweet corn (called Papoon) to European settlers in 1779. It soon became a popular food in southern and central regions of the United States.
Open pollination
Open pollination is pollination by insects, birds, wind, or other natural mechanisms, and contrasts with cleistogamy, closed pollination, which is one of the many types of self pollination...
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
Shoepeg corn
Shoepeg corn is a cultivar of white sweetcorn valued for its sweetness. It is characterized by small, narrow kernels tightly and unevenly packed on the cob. The corn has a sweet, mild flavor. The only variety of shoepeg corn available today is Country Gentleman.Shoepeg corn is popular in some...
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
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
of the sweet corn plant is the corn kernel, a type of fruit called a caryopsis
Caryopsis
In botany, a caryopsis is a type of simple dry fruit — one that is monocarpelate and indehiscent and resembles an achene, except that in a caryopsis the pericarp is fused with the thin seed coat....
. 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
Husk
Husk in botany is the outer shell or coating of a seed. It often refers to the leafy outer covering of an ear of maize as it grows on the plant. Literally, a husk or hull includes the protective outer covering of a seed, fruit or vegetable...
. Silk is the name for 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 AmericaLatin America
Latin America is a region of the Americas where Romance languages – particularly Spanish and Portuguese, and variably French – are primarily spoken. Latin America has an area of approximately 21,069,500 km² , almost 3.9% of the Earth's surface or 14.1% of its land surface area...
, sweet corn is traditionally eaten with beans; each plant is deficient in an essential amino acid
Essential amino acid
An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet.-Essentiality vs. conditional essentiality in humans:...
that happens to be abundant in the other, so together sweet corn and beans form a balanced diet. Similarly, sweet corn in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
is traditionally ground or soaked with milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...
, which makes available a B vitamin
B vitamins
B vitamins are a group of water-soluble vitamins that play important roles in cell metabolism. The B vitamins were once thought to be a single vitamin, referred to as vitamin B . Later research showed that they are chemically distinct vitamins that often coexist in the same foods...
in the corn, the absence of which would otherwise lead to pellagra
Pellagra
Pellagra is a vitamin deficiency disease most commonly caused by a chronic lack of niacin in the diet. It can be caused by decreased intake of niacin or tryptophan, and possibly by excessive intake of leucine. It may also result from alterations in protein metabolism in disorders such as carcinoid...
.
The kernels are boiled or steamed. In Europe, China, Korea, and Japan, they are often used as a pizza
Pizza
Pizza is an oven-baked, flat, disc-shaped bread typically topped with a tomato sauce, cheese and various toppings.Originating in Italy, from the Neapolitan cuisine, the dish has become popular in many parts of the world. An establishment that makes and sells pizzas is called a "pizzeria"...
topping, or in salads. Corn on the cob
Corn on the cob
Corn on the cob is a culinary term used for a cooked ear of freshly picked maize from a cultivar of sweet corn. The ear is picked while the endosperm is in the "milk stage" so that the kernels are still tender...
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
Creamed corn
Creamed corn is a soup or sauce made by melting butter and adding flour, milk, canned corn, and optionally some spices. It is a common part of Midwestern American cuisine, typically sold canned by firms such as Del Monte Foods...
is sweet corn served in a milk or cream sauce. Sweet corn can also be eaten as baby corn
Baby corn
Baby corn or candle corn is a cereal grain taken from corn harvested early while the ears are very small and immature. It typically is eaten whole–cob included—in contrast to mature corn, whose cob is considered too tough for human consumption. Baby corn is eaten both raw and cooked. Baby corn is...
.
If left to dry on the plant, kernels may be taken off the pole and cooked in oil where, unlike popcorn
Popcorn
Popcorn, or popping corn, is corn which expands from the kernel and puffs up when heated. Corn is able to pop because, like sorghum, quinoa and millet, its kernels have a hard moisture-sealed hull and a dense starchy interior. This allows pressure to build inside the kernel until an explosive...
, they expand to about double the original kernel size and are often called corn nut
Corn nut
Corn nuts, also known as toasted corn or corn bits, is a snack food made of roasted or deep-fried corn kernels.- Preparation :Corn nuts are prepared by soaking whole corn kernels in water for three days, then deep-frying them in oil until they are hard and brittle.The kernels are soaked because...
s. A soup may also be made from the plant, called sweet corn soup.
Health benefits
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
activity, which has been suggested to reduce the chance of heart disease
Heart disease
Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...
and cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, although this has not been definitively proven in practice. "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
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
," says Rui Hai Liu assistant professor of food science
Food science
Food science is a study concerned with all technical aspects of foods, beginning with harvesting or slaughtering, and ending with its cooking and consumption, an ideology commonly referred to as "from field to fork"...
at Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
. 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
Ferulic acid
Ferulic acid is a hydroxycinnamic acid, a type of organic compound. It is an abundant phenolic phytochemical found in plant cell wall components such as arabinoxylans as covalent side chains. It is related to trans-cinnamic acid. As a component of lignin, ferulic acid is a precursor in the...
, which provides health benefits, such as battling cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
. "When you cook it, you release it, and what you are losing in vitamin C, you are gaining in ferulic acid and total antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
activity."
Varieties
Genetics
Early varieties, including those used by Native Americans, were the result of the mutant su ("sugary") alleleAllele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
. They contain about 5-10% sugar by weight.
Supersweet corn are varieties of sweet corn which produce higher than normal levels of sugar developed by University of Illinois at Urbana–Champaign professor John Laughnan. He was investigating two specific genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
in sweet corn, one of which, the sh2 gene, caused the corn to shrivel when dry. After further investigation Laughnan discovered that the endosperm of sh2 sweet corn kernels store less 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 1980s. 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.
All of the alleles responsible for sweet corn are recessive
Recessive
In genetics, the term "recessive gene" refers to an allele that causes a phenotype that is only seen in a homozygous genotype and never in a heterozygous genotype. Every person has two copies of every gene on autosomal chromosomes, one from mother and one from father...
, so it must be isolated from any field corn varieties that release pollen at the same time; the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...
develops from genes from both parents, and heterozygous kernels will be tough and starchy. The se and su alleles do not need to be isolated from each other. However supersweet varieties containing the sh2 allele must be grown in isolation from other varieties to avoid cross-pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
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. Generally these brands or trademarks will offer a choice of white, bi-color and yellow varieties which otherwise have very similar characteristics.
Bt corn
Bt corn is genetically modifiedGenetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
to resist certain insects. 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 to protocols that must be followed in their production.
See also
- List of sweetcorn varieties
- CornbreadCornbreadCornbread is a generic name for any number of quick breads containing cornmeal and leavened by baking powder.-History:Native Americans were using ground corn for food thousands of years before European explorers arrived in the New World...
- CornmealCornmealCornmeal is flour ground from dried maize or American corn. It is a common staple food, and is ground to fine, medium, and coarse consistencies. In the United States, the finely ground cornmeal is also referred to as cornflour. However, the word cornflour denotes cornstarch in recipes from the...
- Creamed cornCreamed cornCreamed corn is a soup or sauce made by melting butter and adding flour, milk, canned corn, and optionally some spices. It is a common part of Midwestern American cuisine, typically sold canned by firms such as Del Monte Foods...
- Frozen vegetablesFrozen vegetablesFrozen vegetables may be commercially packaged or frozen at home. A wide range of frozen vegetables are sold in supermarkets, usually packaged in either rectangular boxes or plastic bags....
- Corn syrupCorn syrupCorn syrup is a food syrup, which is made from the starch of maize and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor...