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Scientific classification
Kingdom: Plantae
Division: Angiosperms
Class: Monocots
Order: Asparagales
Family: Alliaceae
Genus: Allium
Species: A. cepa
Binomial name
Allium cepa
Allium cepa var. proliferum, Top Onion

Onion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa.[1] Allium cepa is also known as the "garden onion" or "bulb" onion. It is grown underground by the plant as a vertical shoot that is used for food storage, leading to the possibility of confusion with a tuber, which it is not.

Allium cepa is known only in cultivation,[2] 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.[3] However Zohary and Hopf warn that "there are doubts whether the vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."[4]



Onions, one of the oldest vegetables, are found in a large number of recipes and preparations spanning almost the totality of the world's cultures. They are now available in fresh, frozen, canned, caramelized, pickled, powdered, chopped, and dehydrated forms. Onions can be used, usually chopped or sliced, in almost every type of food, including cooked foods and fresh salads and as a spicy garnish. They are rarely eaten on their own, but usually act as accompaniment to the main course. Depending on the variety, an onion can be sharp, spicy, tangy and pungent or mild and sweet.

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 and Australia, and are referred to simply as "pickled onions". Onions are widely used in Iran and India and Pakistan, and are fundamental in the local cuisine. They are commonly used as a base for curries or made into a paste and eaten as a main course or as a side dish.

Tissue from onions is frequently used in science education to demonstrate microscope usage, because they have particularly large cells that are readily observed even at low magnifications.[5]

Onion powder

Onion powder is a spice used for seasoning in cooking. It is made from finely ground dehydrated onions, mainly the pungent varieties of bulb onions, which causes the powder to have a very strong smell.

Onion powder comes in a few varieties:

  • White onion powder
  • Red onion powder
  • Yellow onion powder
  • Toasted onion powder

Onion powder is toxic to dogs.[6]

Historical uses

It is thought that bulbs from the onion family have been used as a food source for millennia. In Bronze Age settlements, traces of onion remains were found alongside fig and date stones dating back to 5000 BC.[7]

However, it is not clear if these were cultivated onions. Archaeological and literary evidence such as the Book of Numbers 11:5 suggests cultivation probably took place around two thousand years later in ancient Egypt, at the same time that leeks and garlic were cultivated. Workers who built the Egyptian pyramids may have been fed radishes and onions.[7]

The onion is easily propagated, transported and stored. The Ancient Egyptians worshipped it,[8] believing that 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.

In ancient Greece, athletes ate large quantities of onion because it was believed that it would lighten the balance of blood. Roman gladiators were rubbed down with onion to firm up their muscles. In the Middle Ages, onions were such an important food that people would pay their rent with onions, and even give them as gifts.[8] Doctors were known to prescribe onions to facilitate bowel movements and erections, and also to relieve headaches, coughs, snake bite and hair loss. The onion was introduced to North America by Christopher Columbus on his 1492 expedition to Hispaniola. Onions were also prescribed by doctors in the early 1500s to help with infertility in women, and even dogs and cattle and many other household pets. However, recent evidence has shown that dogs, cats, and other animals should not be given onions in any form, due to toxicity during digestion.[9]

Medicinal properties and health effects

Raw Onions
Nutritional value per 100 g (3.5 oz)
Energy 166 kJ (40 kcal)
Carbohydrates 9.34 g
Sugars 4.24 g
Dietary fiber 1.7 g
Fat 0.1 g
saturated 0.042 g
monounsaturated 0.013 g
polyunsaturated 0.017 g
Protein 1.1 g
Water 89.11 g
Vitamin A equiv. 0 μg (0%)
Thiamine (Vit. B1) 0.046 mg (4%)
Riboflavin (Vit. B2) 0.027 mg (2%)
Niacin (Vit. B3) 0.116 mg (1%)
Vitamin B6 0.12 mg (9%)
Folate (Vit. B9) 19 μg (5%)
Vitamin B12 0 μg (0%)
Vitamin C 7.4 mg (12%)
Vitamin E 0.02 mg (0%)
Vitamin K 0.4 μg (0%)
Calcium 23 mg (2%)
Iron 0.21 mg (2%)
Magnesium 0.129 mg (0%)
Phosphorus 29 mg (4%)
Potassium 146 mg (3%)
Sodium 4 mg (0%)
Zinc 0.17 mg (2%)
Percentages are relative to US recommendations for adults.
Source: USDA Nutrient database

Wide-ranging claims have been made for the effectiveness of onions against conditions ranging from the common cold to heart disease, diabetes, osteoporosis, and other diseases.[10] They contain chemical compounds believed to have anti-inflammatory, anticholesterol, anticancer, and antioxidant properties such as quercetin. However, it has not been conclusively demonstrated that increased consumption of onions is directly linked to health benefits. Some studies have shown that increased consumption of onions reduces the risk of head and neck cancers.[11] In India some sects do not eat onion due to its alleged aphrodisiac properties.[12]

In many parts of the world, onions are used to heal blisters and boils. A traditional Maltese remedy for sea urchin wounds is to tie half a baked onion to the afflicted area overnight. An application of raw onion is also said to be helpful in reducing swelling from bee stings. In the United States, products that contain onion extract are used in the treatment of topical scars; some studies have found their action to be ineffective,[13][14][15] while others found that they may act as an anti-inflammatory or bacteriostatic[16] and can improve collagen organization in rabbits.[17]

Onions may be especially beneficial for women,[18] who are at increased risk for osteoporosis as they go through menopause, by destroying osteoclasts so that they do not break down bone.

An American chemist has stated[19] that the pleiomeric chemicals in onions have the potential to alleviate or prevent sore throat. However onion in combination with jaggery has been widely used as a traditional household remedy for sore throat in India.

Shallots have the most phenols, six times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also have the most antioxidant activity, followed by Western Yellow, pungent yellow (New York Bold[20]), Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia. Western Yellow onions have the most flavonoids, 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 antioxidant and anti-cancer activity they provide. When tested against liver and colon cancer cells, Western Yellow, pungent yellow (New York Bold[20]) and shallots were most effective in inhibiting their growth. The milder-tasting varieties—Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia—showed little cancer-fighting ability.[20]

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 benefits of their milder cousins.[20]

Eye irritation

As onions are sliced or eaten, cells are broken, allowing enzymes called alliinases to break down amino acid 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, a volatile gas known as the onion lachrymatory factor or LF.[1] 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 to dilute and flush out the irritant.[21] Chemicals that exhibit such an effect on the eyes are known as lachrymatory agents.

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.[21] Rinsing the onion and leaving it wet while chopping may also be effective. 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.[22] 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 may be avoided by having a fan blow the gas away from the eyes as the onion is being cut.

It is also possible to avoid eye irritation by wearing goggles or any eye protection that creates a seal around the eye. Contact lens wearers can experience less immediate irritation as a result of the slight protection afforded by the lenses themselves. It may[citation needed] also be that lens wearers are familiar with controlling the more reflexive actions of their eyes with regards to irritation; as this is an ability they require when manipulating the lenses to prevent blinking.

The amount of sulfenic acids and LF released, and the irritation effect, differs among Allium species. On January 31, 2008, the New Zealand Crop and Food institute created a strain of "no tears" onions by using gene-silencing biotechnology to prevent synthesis by the onions of the lachyrmatory factor synthase enzyme.[23]


Onion and shallot output in 2005
Onion growing shoots

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 onions, which are the leaves of immature plants. Green onion is a name also used to refer to another species, Allium fistulosum, the Welsh onion, which is said not to produce dry bulbs.

The tree onion produces bulbs instead of flowers and seeds, which can be planted directly in the ground.


  • Bulb onion – Grown from seed (or onion sets), bulb onions range from the pungent varieties used for dried soups and onion powder to the mild and hearty sweet onions, such as the Vidalia from Georgia or Walla Walla from Washington that can be sliced and eaten on a sandwich instead of meat.
  • Multiplier onions – May refer to perennial green onions, or to onions raised from bulbs that produce multiple shoots, each of which forms a bulb. The second type is often referred to as a potato onion.
  • Tree onion or Egyptian onion - Produce bulblets in the flower head; a hybrid of Allium cepas.
  • Welsh onion – Sometimes referred to as green onion or spring onion, although these onions may refer to any green onion stalk.
  • Leek
  • Yellow onion - generally tapered ends, brown skin over the onion, usually sold in 3 lb bags of yellow webbed plastic.
  • Sweet onion - flatter ends and sold individually. Spanish and Vidalia

Production trends

Onion field during harvest, Vale, Oregon (USA).
Top Ten Onion Producers — 2005
(1000 tonnes)
 India 9,793
 China 5,500
 Australia 4,003
 United States 3,346
 Turkey 2,220
 Pakistan 1,764
 Russia 1,758
 South Korea 1,750
 Japan 1,637
 Spain 1,149
World Total 64,101
UN Food & Agriculture Organisation (FAO)

The Onion Futures Act, passed in 1958, bans the trading of futures contracts on onions in the United States, after farmers complained about alleged market manipulation at the Chicago Mercantile Exchange. It provides economists with a unique case study in the effects of futures trading on agricultural prices. It remains in effect as of 2009.

River Point Farms is America's largest grower, packer, shipper and processor of onions; including yellow, white, red, sweet and organic onions.

Aroma attributes

  • 3-Mercapto-2-methylpentan-1-ol[25][26]

Potential medicinal use

3-mercapto-2-methylpentan-1-ol in onion was found to have an antioxidant potent that inhibits peroxynitrite induced diseases.[27]


See also


  1. ^ a b Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
  2. ^ "Allium cepa Linnaeus". Flora of North America. 
  3. ^ Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.
  4. ^ Daniel Zohary and Maria Hopf, Domestication of plants in the Old World, third edition (Oxford: University Press, 2000), p. 198
  5. ^ "Genetics Teaching Vignettes: Elementary School". 2004-06-15. Retrieved 2008-01-28. 
  6. ^ Susan McKay (April 2009). "Canine Queries". Dogs Monthly (ABM): p.97. 
  7. ^ a b "Onions Allium cepa". Retrieved 2006-04-02. 
  8. ^ a b "About Onions: History". Retrieved 2008-01-30. 
  9. ^ "Human Foods that Poison Pets". Retrieved 2008-01-30. 
  10. ^ "World's Healthiest Foods". 2006-06-06. Retrieved 2009-09-04. 
  11. ^ "Onion and garlic use and human cancer. (The American Journal of Clinical Nutrition)". 2006-11-01. Retrieved 2009-09-04. 
  12. ^ Simoons, Frederick (1998). Plants of life, plants of death. Univ of Wisconsin Press. p. 568. ISBN 0299159043.,+plants+of+death+++bibliography&source=bl&ots=x1P06LAlHP&sig=hQsAKHTQMdX__CWBjCFwLCUod6E&hl=en&ei=PhdcSr6gD4HesQPY0vmrCg&sa=X&oi=book_result&ct=result&resnum=1. Retrieved 2009-07-13. 
  13. ^ "Product Review: Mederma for Scars". Retrieved 2009-09-04. 
  14. ^ "Topical scar modification: Hype or help?. (Aesthetic Surgery Journal)". Retrieved 2009-09-04. 
  15. ^ Zurada JM, Kriegel D, Davis IC (2006). "Topical treatments for hypertrophic scars.". Journal of the American Academy of Dermatology 55 (6): 1024–1031. doi:10.1016/j.jaad.2006.03.022. PMID 17097399. 
  16. ^ K. Augusti, Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.), Indian J Exp Biol 34 (1996), pp. 634–640.
  17. ^ Saulis, Alexandrina S. M.D.; Mogford, Jon H. Ph.D.; Mustoe, Thomas A. M.D. (2002). "Effect of Mederma on Hypertrophic Scarring in the Rabbit Ear Model". Plastic and Reconstructive Surgery 110 (1): 177–183. doi:10.1097/00006534-200207000-00029. PMID 12087249. 
  18. ^ "Onion Compound May Help Fight Osteoporosis". 2005-04-11. Retrieved 2008-01-30. 
  19. ^ Chemical & Engineering News Vol. 85 No. 35, 1 Sept. 2008, "Letters", p. 7
  20. ^ a b c d "Onion a day keeps doctor away? (funded by the New York State Department of Agriculture and Markets)" (hmtl). Cornell University. 2004-10-07. Retrieved 2008-01-30. 
  21. ^ a b Scott, Thomas. "What is the chemical process that causes my eyes to tear when I peel an onion?". Ask the Experts: Chemistry. Scientific American. Retrieved 2007-04-28. 
  22. ^ "FAQ". Retrieved 2009-09-04. 
  23. ^ Staunton, Margot (2008-02-01). ", Scientists create 'no tears' onions".,23599,23144566-23109,00.html. Retrieved 2009-09-04. 
  24. ^
  25. ^ Widder, Sabine et al. (2000). "3-Mercapto-2-methylpentan-1-ol, a New Powerful Aroma Compound". Journal of Agricultural and Food Chemistry 48 (2): 418 – 423. doi:10.1021/jf9908291. 
  26. ^ Granvog, Michael et al. (2004). "Quantitation of the Intense Aroma Compound 3-Mercapto-2-methylpentan-1-ol in Raw and Processed Onions (Allium cepa) of Different Origins and in Other Allium Varieties Using a Stable Isotope Dilution Assay". Journal of Agricultural and Food Chemistry 52 (10): 2797–2802. doi:10.1021/jf049874l. 
  27. ^ Rose, Peter et al. (2003). "Inhibition of peroxynitrite-mediated cellular toxicity, tyrosine nitration, and α1-antiproteinase inactivation by 3-mercapto-2-methylpentan-1-ol, a novel compound isolated from Allium cepa". Biochemical and Biophysical Research Communications 302 (2): 397–402. doi:10.1016/S0006-291X(03)00193-1. 


External links

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

ONION (Fr. oignon, Lat. unio, liberally unity, oneness, applied to a large pearl and to a species of onion), Allium Cepa (nat. ord. Liliaceae), a hardy bulbous biennial, which has been cultivated in Britain from time immemorial, and is one of the earliest of cultivated species; it is represented on Egyptian monuments, and one variety cultivated in Egypt was accorded divine honours. It is commonly cultivated in India, China and Japan. A. de Candolle, arguing from its ancient cultivation and the antiquity of the Sanskrit and Hebrew names, regards it as a native of western Asia.

The onion should be grown in an open situation, and on a light, rich, well-worked soil, which has not been recently manured. In England the principal crop may be sown at any time from the middle of February to the middle of March, if the weather is fine and the ground sufficiently dry. The seed should be sown in shallow drills, 10 in. apart, the ground being made as level and firm as possible, and the plants should be regularly thinned, hoed and kept free from weeds. At the final thinning they should be set from 3 to 6 in. apart, the latter distance in very rich soil. About the beginning of September the crop is ripe, which is known by the withering of the leaves; the bulbs are then to be pulled, and exposed on the ground till well dried, and they are then to be put away in a store-room, or loft, where they may be perfectly secured from frost and damp.

About the end of August a crop is sown to afford a supply of young onions in the spring months. Those which are not required for the kitchen, if allowed to stand, and if the flower-bud is picked out on its first appearance, and the earth stirred about them, frequently produce bulbs equal in size and quality to the large ones that are imported from the Continent. A crop of very large bulbs may also be secured by sowing about the beginning of September, and transplanting early in spring to very rich soil. Another plan is to sow in May on dry poor soil, when a crop of small bulbs will be produced; these are to be stored in the usual way, and planted in rich soil about February, on ground made firm by treading, in rows about 1 ft. apart, the bulbs being set near the surface, and about 6 in. asunder. The White Spanish and Tripoli are good sorts for this purpose.

To obtain a crop of bulbs for pickling, seed should be sown thickly in March, in rather poor soil, the seeds being very thinly covered, and the surface well rolled; these are not to be thinned, but should be pulled and harvested when ripe. The best sorts for this crop are the Silver-skinned, Early Silver-skinned, Nocera and Queen.

Onions may be forced like mustard and cress if required for winter salads, the seeds being sown thickly in boxes which are to be placed in a warm house or frame. The young onions are of course pulled while quite small.

The Potato Onion, Allium Cepa var. aggregatum, is propagated by the lateral bulbs, which it throws out, under ground, in considerable numbers. This variety is very prolific, and is useful when other sorts do not keep well. It is sometimes planted about midwinter, and then ripens in summer, but for use during the spring and early summer it is best planted in spring. It is also known as the underground onion, from its habit of producing its bulbs beneath the surface.

The Tree Onion or Egyptian Onion, Allium Cepa var. proliferum, produces small bulbs instead of flowers, and a few offsets also underground. These small stem bulbs are excellent for pickling.

The Welsh Onion or Ciboule, Allium fistulosum, is a hardy perennial, native of Siberia. It was unknown to the ancients, and must have come into Europe through Russia in the middle ages or later. It forms no bulbs, but, on account of its extreme hardiness, is sown in July or early in August, to furnish a reliable supply of young onions for use in salads during the early spring. These bulbless onions are sometimes called Scallions, a name which is also applied to old onions which have stem and leaves but no bulbs.

The following are among the best varieties of onions for various purposes For Summer and Autumn. - Queen; Early White Naples: these two sorts also excellent for sowing in autumn for spring salading. Silver-skinned; Tripoli, including Giant Rocca.

For Winter

Brown Globe, including Magnum Bonum; White Globe; Yellow Danvers; White Spanish, in its several forms; Trebons, the finest variety for autumn sowing, attaining a large size early, ripening well, and keeping good till after Christmas; Ailsa Craig; Ronsham Park Hero; James's Keeping; Cranston's Excelsior; Blood Red, strong-flavoured.

For Pickling

Queen, Early Silver-skinned, White Nocera, Egyptian.

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Bible wiki

Up to date as of January 23, 2010

From BibleWiki

The Israelites in the wilderness longed for the "onions and garlick of Egypt" (Num. 11:5). This was the betsel of the Hebrews, the Allium cepe of botanists, of which it is said that there are some thirty or forty species now growing in Palestine. The onion is "the 'undivided' leek, unio_, _unus, one."

This entry includes text from Easton's Bible Dictionary, 1897.

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Simple English

Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Liliopsida
Order: Asparagales
Family: Alliaceae
Genus: Allium
Species: A. cepa
Binomial name
Allium cepa

Onions are vegetables. They are plants in the genus Allium. When people talk about onions, they usually mean garden onions. Onions have bulbs, which are edible, in most species. They have a strong flavour, and a very distinctive smell.

Onions have been grown for a very long time. Together with leek and garlic, they go back to Ancient Egypt at least.

How onions are eaten

Onions can be eaten in different ways. Fried onions are often served with hot dogs. Pickled onions are eaten with chips or with salad. Raw onions are sliced (cut into flat layers) for hamburgers. Chopped onions are put in many stews and curries. Onions are sometimes roasted whole.


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