Onion - AbsoluteAstronomy.com

The onion also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium
Allium
Allium is a monocot genus of flowering plants, informally referred to as the onion genus. The generic name Allium is the Latin word for garlic....

. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion (A. fistulosum), Egyptian onion (A. ×proliferum), and Canada onion (A. canadense). The name "wild onion

Wild onion

Wild onion can refer to* any uncultivated species in the genus Allium, especially:**Allium bisceptrum** Allium canadense** Allium validum** Allium vineale* Cyperus bulbosus* Bulbine semibarbata...

" is applied to a number of Allium species.

The vast majority of cultivars of A. cepa belong to the 'common onion group' (A. cepa var. cepa) and are usually referred to simply as 'onions'. The 'Aggregatum group' of cultivars (A. cepa var. aggregatum) includes both shallots and potato onion

Potato onion

The potato onion is a variety of the 'Aggregatum group' of Allium cepa, similar to the shallot, although producing larger bulbs. It is remarkably easy to grow, keeps better than almost any other variety of onion, and is ideal for the home gardener with restricted space...

s.

Allium cepa is known only in cultivation, but related wild species occur in Central Asia. The most closely related species include Allium vavilovii (Popov & Vved.) and Allium asarense (R.M. Fritsch & Matin) from Iran

Iran

Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

. However, Zohary and Hopf warn that "there are doubts whether the A. vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."

Culinary uses

Onions are often chopped and used an ingredient in various hearty warm dishes, although onions can also be a more prominent ingredient, for example in French onion soup

French onion soup

French onion soup is an onion and beef broth or a beef stock based soup traditionally served with croutons and cheese as toppings...

, or be used raw in cold salads. Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

and Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, often served with cheese

Cheese

Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

in the United Kingdom

United Kingdom

, and are referred to simply as "pickled onion

Pickled onion

Pickled onions are a popular pickled food consisting of onions pickled in a solution of vinegar and salt, often with other preservatives and flavourings. In the United Kingdom they are often eaten alongside fish and chips or as part of a ploughman's lunch...

s" in Eastern Europe.

Onion types and products

Common onions are normally available in three colors: yellow, red, and white. Yellow onions are full-flavored and are a reliable standby for cooking almost anything. Yellow onions turn a rich, dark brown when cooked and give French onion soup its tangy sweet flavor. The red onion is a good choice for fresh uses or in grilling and char-broiling. White onions are the traditional onion used in classic Mexican cuisine. They have a golden color and sweet flavor when sautéed.

While the large mature onion bulb is the onion most often eaten, onions can be eaten at immature stages. Young plants may be harvested before bulbing occurs and used whole as scallions. When an onion is harvested after bulbing has begun but the onion is not yet mature, the plants are sometimes referred to as summer onions.

Additionally, onions may be bred and grown to mature at smaller sizes. Depending on the mature size and the purpose for which the onion is used, these may be referred to as pearl, boiler, or pickler onions. (However, true pearl onion

Pearl onion

The "true" pearl onion is a close relative of leek , and may be distinguished from bulb onions by having only a single storage leaf, similar to cloves of garlic...

s are a different species.) Pearl and boiler onions may be cooked as a vegetable rather than an ingredient. Pickler onions are, unsurprisingly, often pickled.

Onion seed may be "sprouted", and the resulting sprouts used in salads, sandwiches, and other dishes. (See sprouting

Sprouting

Sprouting is the practice of germinating seeds to be eaten either raw or cooked.They are a convenient way to have fresh vegetables for salads, or otherwise, in any season and can be germinated at home or produced industrially...

.)

Onions are available in fresh, frozen, canned, caramelized

Caramelization

Caramelization is the browning of sugar, a process used extensively in cooking for the resulting nutty flavor and brown color. As the process occurs, volatile chemicals are released, producing the characteristic caramel flavor....

, pickled, powdered, chopped, and dehydrated forms.

Onion powder is a spice

Spice

A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...

used for seasoning in cooking

Cooking

Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...

. It is made from finely ground, dehydrated onions, mainly the pungent varieties of bulb onions, which causes the powder to have a very strong odor. Onion powder comes in a few varieties: white, yellow, red and toasted.

Non-culinary uses

Onions have particularly large cells that are readily observed at low magnification; consequently, onion tissue is frequently used in science education

Science education

Science education is the field concerned with sharing science content and process with individuals not traditionally considered part of the scientific community. The target individuals may be children, college students, or adults within the general public. The field of science education comprises...

for demonstrating microscope

Microscope

A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

usage.

Onion skins have been used for dye.

Historical uses

Bulbs from the onion family are thought to have been used as a food source for millennia. In Bronze Age

Bronze Age

The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

settlements, traces of onion remains were found alongside fig

Ficus

Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The Common Fig Ficus is a genus of...

and date

Date Palm

The date palm is a palm in the genus Phoenix, cultivated for its edible sweet fruit. Although its place of origin is unknown because of long cultivation, it probably originated from lands around the Persian Gulf. It is a medium-sized plant, 15–25 m tall, growing singly or forming a clump with...

stones dating back to 5000 BC.

However, it is not clear if these were cultivated onions. Archaeological and literary evidence such as the Book of Numbers

Book of Numbers

The Book of Numbers is the fourth book of the Hebrew Bible, and the fourth of five books of the Jewish Torah/Pentateuch....

11:5 suggests cultivation probably took place around two thousand years later in ancient Egypt

Ancient Egypt

Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...

, at the same time that leeks and garlic

Garlic

Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...

were cultivated. Workers who built the Egyptian pyramids

Egyptian pyramids

The Egyptian pyramids are ancient pyramid-shaped masonry structures located in Egypt.There are 138 pyramids discovered in Egypt as of 2008. Most were built as tombs for the country's Pharaohs and their consorts during the Old and Middle Kingdom periods.The earliest known Egyptian pyramids are found...

may have been fed radish

Radish

The radish is an edible root vegetable of the Brassicaceae family that was domesticated in Europe, in pre-Roman times. They are grown and consumed throughout the world. Radishes have numerous varieties, varying in size, color and duration of required cultivation time...

es and onions.

The onion is easily propagated, transported and stored. The ancient Egypt

Ancient Egypt

ians worshipped it, believing its spherical shape and concentric rings symbolized eternal life. Onions were even used in Egyptian burials, as evidenced by onion traces being found in the eye sockets of Ramesses IV

Ramesses IV

Heqamaatre Ramesses IV was the third pharaoh of the Twentieth Dynasty of the New Kingdom of Ancient Egypt. His name prior to assuming the crown was Amonhirkhopshef...

.

In ancient Greece

Ancient Greece

Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, athletes ate large quantities of onion because it was believed to lighten the balance of blood. Roman gladiator

Gladiator

A gladiator was an armed combatant who entertained audiences in the Roman Republic and Roman Empire in violent confrontations with other gladiators, wild animals, and condemned criminals. Some gladiators were volunteers who risked their legal and social standing and their lives by appearing in the...

s were rubbed down with onion to firm up their muscles. In the Middle Ages

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, onions were such an important food that people would pay their rent with onions, and even give them as gifts. Doctors were known to prescribe onions to facilitate bowel movements and erections, and also to relieve headaches, coughs, snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

bite and hair loss.

The cultivated onion was introduced to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

by Christopher Columbus

Christopher Columbus

Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

on his 1492 expedition to Hispaniola

Hispaniola

Hispaniola is a major island in the Caribbean, containing the two sovereign states of the Dominican Republic and Haiti. The island is located between the islands of Cuba to the west and Puerto Rico to the east, within the hurricane belt...

; however, they found that strains of wild onions already grew throughout North America. Native American Indians used wild onions in a variety of ways, eating them raw or cooked, as a seasoning or as a vegetable. Such onions were also used in syrups, as poultices, as an ingredient in dyes and even as toys. According to diaries of colonists, bulb onions were planted as soon as the Pilgrim fathers could clear the land in 1648.

Onions were also prescribed by doctors in the early 16th century to help with infertility in women, and even dogs, cats and cattle and many other household pets. However, recent evidence has shown that dogs, cats, guinea pigs, and other animals should not be given onions in any form, due to toxicity during digestion.

Medicinal properties and health effects of onions

Wide-ranging claims have been made for the effectiveness of onions against conditions ranging from the common cold to heart disease, diabetes, osteoporosis

Osteoporosis

Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...

, and other diseases. They contain chemical compounds believed to have anti-inflammatory

Anti-inflammatory

Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....

, anticholesterol, anticancer, and 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...

properties, such as quercetin

Quercetin

Quercetin , a flavonol, is a plant-derived flavonoid found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.-Occurrence:...

. Preliminary studies have shown increased consumption of onions reduces the risk of head and neck cancers.

Among all varieties, Asian white onions have the most eye irritating chemical reaction. Regular use of white onion, if eaten raw, is claimed to be good due to its antioxidant

Antioxidant

and anti-inflammatory

Anti-inflammatory

properties.

In India some sects do not eat onions as they believe them to be an aphrodisiac

Aphrodisiac

An aphrodisiac is a substance that increases sexual desire. The name comes from Aphrodite, the Greek goddess of sexuality and love. Throughout history, many foods, drinks, and behaviors have had a reputation for making sex more attainable and/or pleasurable...

; various schools of Buddhism also advise against eating onions and other vegetables of the Allium family.

In many parts of the undeveloped world, onions are used to heal blisters and boils. A traditional Maltese

Malta

Malta , officially known as the Republic of Malta , is a Southern European country consisting of an archipelago situated in the centre of the Mediterranean, south of Sicily, east of Tunisia and north of Libya, with Gibraltar to the west and Alexandria to the east.Malta covers just over in...

remedy for sea urchin

Sea urchin

Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

wounds is to tie half a baked onion to the afflicted area overnight. A similar traditional cure is known in Bulgaria. Half-baked onion with sugar is placed over the finger and fingernail in case of inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

.

An application of raw onion is also said to be helpful in reducing swelling from bee sting

Bee sting

A bee sting is strictly a sting from a bee . In the vernacular it can mean a sting of a bee, wasp, hornet, or yellow jacket. Some people may even call the bite of a horse-fly a bee sting...

s. In the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, products that contain onion extract are used in the treatment of topical scars; some studies have found their action to be ineffective, while others found that they may act as an anti-inflammatory or bacteriostatic and can improve collagen organization in rabbits.

Onions may be beneficial for women, who are at increased risk for osteoporosis

Osteoporosis

as they go through menopause, by destroying osteoclasts so they do not break down bone.

An American chemist has stated the pleiomeric chemicals in onions have the potential to alleviate or prevent sore throat

Pharyngitis

Pharyngitis is an inflammation of the throat or pharynx. In most cases it is quite painful, and is the most common cause of a sore throat.Like many types of inflammation, pharyngitis can be acute – characterized by a rapid onset and typically a relatively short course – or chronic....

. Onion in combination with jaggery

Jaggery

Jaggery is a traditional unrefined non-centrifugal whole cane sugar consumed in Asia, Africa, Latin America, and the Caribbean. It is a concentrated product of cane juice without separation of the molasses and crystals, and can vary from golden brown to dark brown in color...

has been widely used as a traditional household remedy for sore throat in India.

Shallot

Shallot

The shallot is the botanical variety of Allium cepa to which the multiplier onion also belongs. It was formerly classified as the species A. ascalonicum, a name now considered a synonym of the correct name...

s have the most phenol

Natural phenol

Natural phenols, bioavailable phenols, plant phenolics, low molecular weight phenols or phenoloids are a class of natural products. They are small molecules containing one or more phenolic group. These molecules are smaller in size than polyphenols, containing less than 12 phenolic groups...

s, six times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also have the most antioxidant

Antioxidant

activity, followed by Western Yellow, pungent yellow (New York Bold), Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia. Western Yellow onions have the most flavonoid

Flavonoid

Flavonoids , are a class of plant secondary metabolites....

s, eleven times the amount found in Western White, the variety with the lowest flavonoid content.

For all varieties of onions, the more phenols and flavonoids they contain, the more reputed antioxidant and anticancer activity they provide. When tested against liver and colon cancer cells in laboratory studies, 'Western Yellow', pungent yellow (New York Bold) and shallots were most effective in inhibiting their growth. The milder-tasting cultivars (i.e., 'Western White,' 'Peruvian Sweet,' 'Empire Sweet,' 'Mexico,' 'Texas 1015,' 'Imperial Valley Sweet' and 'Vidalia') showed little cancer-fighting ability.

Shallots and ten other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, pungent yellow (New York Bold), Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia. In general, the most pungent onions delivered many times the effects of their milder cousins.

The 3-mercapto-2-methylpentan-1-ol in onion was found to inhibit peroxynitrite

Peroxynitrite

Peroxynitrite is the anion with the formula ONOO−. It is an unstable structural isomer of nitrate, NO3−, which has the same formula but a different structure. Although peroxynitrous acid is highly reactive, its conjugate base peroxynitrite is stable in basic solution...

-induced mechanisms in vitro.

While members of the onion family appear to have medicinal properties for humans, they can be deadly for dogs, cats, and guinea pigs.

Eye irritation

As onions are sliced or eaten, cells

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

are broken, allowing enzymes called alliinase

Alliinase

In enzymology, an alliin lyase is an enzyme that catalyzes the chemical reactionHence, this enzyme has one substrate, S-alkyl-L-cysteine S-oxide, and two products, alkyl sulfenate and 2-aminoacrylate....

s to break down amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

sulphoxides and generate sulphenic acids. A specific sulfenic acid, 1-propenesulfenic acid, formed when onions are cut, is rapidly rearranged by a second enzyme, called the lachrymatory factor synthase or LFS, giving syn-propanethial-S-oxide

Syn-propanethial-S-oxide

syn-Propanethial S-oxide is a gas that acts as a lachrymatory agent . The chemical is released from onions, Allium cepa, as they are sliced...

, a volatile gas known as the onion lachrymatory factor or LF. The LF gas diffuses through the air and eventually reaches the eye, where it activates sensory neurons, creating a stinging sensation. Tear glands produce tears

Tears

Tears are secretions that clean and lubricate the eyes. Lacrimation or lachrymation is the production or shedding of tears....

to dilute and flush out the irritant. Chemicals that exhibit such an effect on the eyes are known as lachrymatory agent

Lachrymatory agent

Tear gas, formally known as a lachrymatory agent or lachrymator , is a non-lethal chemical weapon that stimulates the corneal nerves in the eyes to cause tears, pain, and even blindness...

s.

Supplying ample water to the reaction while peeling onions prevents the gas from reaching the eyes. Eye irritation can, therefore, be avoided by cutting onions under running water or submerged in a basin of water. Another way to reduce irritation is by chilling, or by not cutting off the root of the onion (or by doing it last), as the root of the onion has a higher concentration of enzymes. Using a sharp blade to chop onions will limit the cell damage and the release of enzymes that drive the irritation response. Chilling or freezing onions prevents the enzymes from activating, limiting the amount of gas generated.

Eye irritation can also be avoided by having a fan blow the gas away from the eyes, or by wearing goggles or any eye protection that creates a seal around the eye. Contact lens

Contact lens

A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...

wearers may also experience less immediate irritation as a result of the slight protection afforded by the lenses themselves.

The amount of sulfenic acids and LF released and the irritation effect differs among Allium species. On January 31, 2008, the New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

Crop and Food institute created a strain of "no tears" onions by using gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

-silencing biotechnology

Biotechnology

Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...

to prevent synthesis by the onions of the lachrymatory factor synthase enzyme.

Propagation

Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants that produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.

Seed-bearing onions are day-length sensitive; their bulbs begin growing only after the number of daylight hours has surpassed some minimal quantity. Most traditional European onions are what is referred to as "long-day" onions, producing bulbs only after 15+ hours of daylight occur. Southern European and North African varieties are often known as "intermediate day" types, requiring only 12–13 hours of daylight to stimulate bulb formation. Finally, "short-day" onions, which have been developed in more recent times, are planted in mild-winter areas in the fall and form bulbs in the early spring, and require only 9–10 hours of sunlight to stimulate bulb formation.

Either planting method may be used to produce spring onions or green onion

Scallion

Scallions , are the edible plants of various Allium species, all of which are "onion-like", having hollow green leaves and lacking a fully developed root bulb.-Etymology:The words...

s, which are the leaves of immature plants. Green onion is a name also used to refer to another species, Allium fistulosum, the Welsh onion

Welsh onion

Allium fistulosum L. is a perennial onion. Other names that may be applied to this plant include green onion, spring onion, escallion, and salad onion...

, which does not form bulbs.

The tree onion

Tree onion

Tree onions, Allium ×proliferum, are similar to common onions, but with a cluster of bulblets where a normal onion would have flowers. Genomic evidence has conclusively shown that they are a hybrid of the common onion and the Welsh onion . However, some sources may still treat the tree onion as A....

produces bulblets instead of flowers and seeds, which can be planted directly in the ground.

I'itoi onion (Allium cepa) is a prolific multiplier onion cultivated near Baboquiviri, Arizona. They have a shallot-like flavor. They are easy to grow and ideal for hot, dry climates. To grow them, separate bulbs, and plant in the fall 1 inch below surface and 12 inches apart. Bulbs will multiply into clumps and can be harvested throughout the cooler months. Tops will die back in the heat of summer and may return with monsoon rains; bulbs can remain in the ground or be harvested and stored in a cool dry place for planting in the fall. The plants rarely flower; propagation is by division.

Common onion group (var. cepa)

Most of the diversity within A. cepa occurs within this group, the most economically important Allium crop. Plants within this group form large single bulbs, and are grown from seed or seed-grown sets. The majority of cultivars grown for dry bulbs, salad onions, and pickling onions belong to this group. The range of diversity found among these cultivars includes variation in photoperiod (length of day that triggers bulbing), storage life, flavour, and skin colour. Common onions range from the pungent varieties used for dried soups and onion powder to the mild and hearty sweet onion

Sweet onion

A sweet onion is a variety of onion that is not pungent. Their mildness is attributable to their low sulfur content and high water content when compared to other onion varieties.-Origins in the United States:...

s, such as the Vidalia

Vidalia onion

A Vidalia onion is a sweet onion of certain varieties, grown in a production area defined by law in Georgia and by the United States Code of Federal Regulations . The varieties include the hybrid yellow granex, varieties of granex parentage, or other similar varieties recommended by the Vidalia...

from Georgia, USA

Georgia (U.S. state)

Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

, or Walla Walla from Washington that can be sliced and eaten on a sandwich instead of meat.

European onions

A number of onions have Protected Geographical Status

Protected Geographical Status

Protected Geographical Status is a legal framework defined in European Union law to protect the names of regional foods. Protected Designation of Origin , Protected Geographical Indication and Traditional Speciality Guaranteed are distinct regimes of geographical indications within the framework...

in Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, these include:

Cipolla Rossa di Tropea, a red onion from Calabria
Calabria
Calabria , in antiquity known as Bruttium, is a region in southern Italy, south of Naples, located at the "toe" of the Italian Peninsula. The capital city of Calabria is Catanzaro....

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

(PGI)
Cipollotto Nocerino, a spring/salad onion-sized Allium Ccepa from Campania
Campania
Campania is a region in southern Italy. The region has a population of around 5.8 million people, making it the second-most-populous region of Italy; its total area of 13,590 km² makes it the most densely populated region in the country...

, Italy (PDO)
Oignon doux des Cévennes, a sweet onion from the south east of France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

(PDO)

Aggregatum group (var. aggregatum)

This group contains shallots and potato onion

Potato onion

s, also referred to as multiplier onions. The bulbs are smaller than those of common onions, and a single plant forms an aggregate cluster of several bulbs. They are propagated almost exclusively from daughter bulbs, although reproduction from seed is possible. Shallots are the most important subgroup within this group and comprise the only cultivars cultivated commercially. They form aggregate clusters of small, narrowly ovoid to pear-shaped bulbs. Potato onions differ from shallots in forming larger bulbs with fewer bulbs per cluster, and having a more flattened (onion-like) shape. However, intermediate forms exist.

Species that may be confused with A. cepa

Scallions or salad onions may be grown from the Welsh onion

Welsh onion

Allium fistulosum L. is a perennial onion. Other names that may be applied to this plant include green onion, spring onion, escallion, and salad onion...

(A. fistulosum) as well as from A. cepa. Young plants of A. fistulosum and A. cepa look very similar, but may be distinguished by their leaves, which are circular in cross-section in A. fistulosum rather than flattened on one side.

Hybrids with A. cepa parentage

A number of hybrids are cultivated that have A. cepa parentage, such as the tree onion

Tree onion

or Egyptian onion (A. ×proliferum), Wakegi onion (A. ×wakegi), and the triploid onion (A. ×cornutum).

Diploid hybrids

The tree onion or Egyptian onion produces bulblets in the flower head instead of flowers, and is now known to be a hybrid of A. cepa × A. fistulosum. It has previously been treated as a variety of A. cepa, for example A. cepa var. proliferum, A. cepa var. bulbiferum, and A. cepa var. viviparum.

The Wakegi onion is also known to be a hybrid between A. cepa and A. fistulosum, with the A. cepa parent believed to be from the 'aggregatum' group of cultivars. It has been grown for centuries in Japan and China for use as a salad onion.

Under the rules of botanical nomenclature

Botanical nomenclature

Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...

, both the Egyptian onion and Wakegi onion should be combined into one hybridogenic species, having the same parent species. Where this is followed, the Egyptian onion is named A. ×proliferum 'Eurasian group' and the Wakegi onion is named A. ×proliferum 'East Asian group'.

Triploid onions

The triploid onion is a hybrid species with three sets of chromosomes, two sets from A. cepa and the third set from an unknown parent. Various clones of the triploid onion are grown locally in different regions, such as 'Ljutika' in Croatia, and 'Pran', 'Poonch' and 'Srinagar' in the India-Kashmir region. 'Pran' is grown extensively in the Northern Indian provinces of Jammu and Kashmir. There are very small genetic differences between 'Pran' and the Croatian clone 'Ljutika', implying a monophyletic origin for this species.

Some authors have used the name A. cepa var. viviparum (Metzg.) Alef. for the triploid onion, but this name has also been applied to the Egyptian onion. The only name unambiguously connected with the triploid onion is A. ×cornutum.

Storage

Green onion and leeks are optimally stored refrigerated. Cooking onions and sweet onions, on the other hand, can be stored at room temperature, optimally in a single layer, in mesh bag in a dry, cool, dark, well ventilated location. In this environment, cooking onions have a shelf life of 3 to 4 weeks, and sweet onions 1 to 2 weeks. Cooking onions will absorb odours from apples and pears. Also, they draw moisture from vegetables they are stored with which may cause them to decay. Sweet onions have a greater water and sugar content than cooking onions. This makes them sweeter and milder tasting, but also reduces their shelf life. Sweet onions can also be stored refrigerated; they have a shelf life of approximately 1 month, optimally uncovered. Irrespective of type, any cut pieces of onion are optimally tightly wrapped, stored away from other produce, and used within 2 to 3 days.

Production trends

Top Ten Onion Producers — 2009 (metric tons)
	21,046,969
	13,900,000
	3,400,560
	1,849,580
	1,800,000
	1,704,100
	1,601,550
	1,512,150
	1,511,850
Netherlands	1,269,000
World Total	73,231,830
Source: UN Food & Agriculture Organisation (FAO)

The Onion Futures Act

Onion Futures Act

The Onion Futures Act is a United States law banning the trading of futures contracts on onions. In 1955 two onion traders, Sam Seigel and Vincent Kosuga, cornered the onion futures market on the Chicago Mercantile Exchange. The resulting regulatory actions led to the passing of the act on August...

, passed in 1958, bans the trading of futures contract

Futures contract

In finance, a futures contract is a standardized contract between two parties to exchange a specified asset of standardized quantity and quality for a price agreed today with delivery occurring at a specified future date, the delivery date. The contracts are traded on a futures exchange...

s on onions in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, after farmers complained about alleged market manipulation

Market manipulation

Market manipulation describes a deliberate attempt to interfere with the free and fair operation of the market and create artificial, false or misleading appearances with respect to the price of, or market for, a security, commodity or currency...

by Sam Seigel and Vincent Kosuga

Vincent Kosuga

Vincent Kosuga was an American onion farmer and commodity trader best known for manipulating the onion futures market. Though he made millions of dollars on commodity trading, his actions were highly controversial and attracted government scrutiny...

at the Chicago Mercantile Exchange

Chicago Mercantile Exchange

The Chicago Mercantile Exchange is an American financial and commodity derivative exchange based in Chicago. The CME was founded in 1898 as the Chicago Butter and Egg Board. Originally, the exchange was a non-profit organization...

. It provides economist

Economist

An economist is a professional in the social science discipline of economics. The individual may also study, develop, and apply theories and concepts from economics and write about economic policy...

s with a unique case study in the effects of futures trading on agricultural prices. It remains in effect .

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Culinary uses

Onion types and products

Non-culinary uses

Historical uses

Medicinal properties and health effects of onions

Eye irritation

Propagation

Common onion group (var. cepa)

European onions

Aggregatum group (var. aggregatum)

Species that may be confused with A. cepa

Hybrids with A. cepa parentage

Diploid hybrids

Triploid onions

Storage

Production trends

See also

External links