Onion | |
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Scientific classification ![]() |
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Kingdom: | Plantae |
Clade: | Angiosperms |
Clade: | Monocots |
Order: | Asparagales |
Family: | Amaryllidaceae |
Subfamily: | Allioideae |
Genus: | Allium |
Species: | A. cepa |
Binomial name | |
Allium cepa L. |
The onion (Allium cepa), which is also known as the bulb onion,[1] common onion[2] is the most widely cultivated species of the genus Allium.[3] 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).[2] The name "wild onion" is applied to a number of Allium species. Onion is most frequently a biennial, although it can also be a triennial or a perennial.
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 onions.[4]
Allium cepa is known exclusively in cultivation,[5] 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.[6] 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."[7]
Contents |
Uses of an onion
Culinary uses
Onions are often chopped and used as an ingredient in various hearty warm dishes, and may also used as a main ingredient in their own right, for example in French onion soup or onion chutney. They are also used raw in cold salads. Onions are also used as a thickening agent for curries providing a bulk of the base. 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, often served with cheese in the United Kingdom, and as "pickled onions" in Eastern Europe. Fresh onion has a pungent, persistent, even irritating taste, but when sautéed, onion becomes sweet and much less pungent.
Onion types and products
Common onions are normally available in three colours: yellow, red, and white. Yellow onions, also called brown onions, are full-flavoured 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 flavour. 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 colour and sweet flavour 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.[8] 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.[9]
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.[9] (However, true pearl onions 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.)
Onions are available in fresh, frozen, canned, caramelized, pickled, powdered, chopped, and dehydrated forms.
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 odour. 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 for demonstrating microscope usage.[10]
Onion skins have been used for dye.[11]
Historical uses
Bulbs from the onion family are thought to have been used as a food source for millennia. In Bronze Age settlements, traces of onion remains were found alongside date stones and fig remains that date back to 5000 BC.[12]
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.[12]
The onion is easily propagated, transported and stored. The ancient Egyptians worshipped it,[13] 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.
In ancient Greece, athletes ate large quantities of onion because it was believed to 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.[13] Doctors were known to prescribe onions to facilitate bowel movements and erections, and also to relieve headaches, coughs, snakebite and hair loss.
The cultivated onion was introduced to North America by Christopher Columbus on his 1492 expedition to Hispaniola; 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.[13]
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.[14][15][16]
Nutrients and potential health effects
Nutritional value per 100 g (3.5 oz) | |
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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 (9%) |
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 |
Onions contain chemical compounds with potential anti-inflammatory, anticholesterol, anticancer, and antioxidant properties, such as quercetin.[17] Shallots have the most phenols, six times the amount found in Vidalia onion, the variety with the lowest phenolic content.[18] Onion extract has been proposed as a means of reducing scars, though this has not proven effective in people with light skin.[19] Urban legends and folk remedies promote the use of cut onions to prevent influenza, though this practice is not actually effective.[20] While members of the onion family are commonly consumed by humans, they can be deadly for dogs, cats, and guinea pigs.[14][15][16] The toxicity is caused by the sulfoxides present in raw and cooked onions, with typical toxic doses of 5 g/kg for cats and 15–30 g/kg for dogs.[14]
In India, some sects do not eat onions as they believe them to be an aphrodisiac.[21] Various schools of Buddhism also advise against eating onions and other related vegetables.[22]
Eye irritation
![](https://web.archive.org/web/20130109154513im_/http://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Cortando_cebolla.jpg/220px-Cortando_cebolla.jpg)
As onions are sliced or eaten, cells are broken, allowing enzymes called alliinases to break down amino acid sulfoxides and generate sulfenic 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.[23] 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.[24] 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.[24] 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.[25] 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 wearers may also experience less immediate irritation as a result of the slight protection afforded by the lenses themselves.[citation needed]
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 lachrymatory factor synthase enzyme.[26]
Propagation
Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion seeds are notoriously short lived.,,[27][28][29] 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 occurs. 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.[27]
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 does not form bulbs.
Onions are a cool-weather plant; hot temperatures cause them to "bolt" (meaning that the stem quickly grows and begins flowering). Since they take up to 120 days to maturity, seeds will often have to be started indoors. The seedlings or bulbs are planted outside as soon as the soil is workable (i.e. not frozen or soggy) and harvested in early summer. Snowfalls in March or April are often known as "onion snows" because they fall on freshly planted onions.
All members of the Allium family are prone to the deadly disease of white rot mildew (typically spread through infected garlic cloves), which can linger in soil for many years and destroys the plants.
The tree onion 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 flavour. They are easy to grow and ideal for hot, dry climates. To grow them, bulbs are separated, and planted 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.
Varieties
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.[4] The range of diversity found among these cultivars includes variation in photoperiod (length of day that triggers bulbing), storage life, flavour, and skin colour.[30] Common 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, USA, 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 in Europe, these include:
- Cebolla Fuentes de Ebro, a sweet, watery and soft variety from Zaragoza, Spain (PDO)
- Cipolla Rossa di Tropea, a red onion from Calabria, Italy (PGI)
- Cipollotto Nocerino, a spring/salad onion-sized Allium cepa from Campania, Italy (PDO)
- Oignon doux des Cévennes, a sweet onion from the southeast of France (PDO)
Aggregatum Group (var. aggregatum)
This group contains shallots and potato onions, 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 flattened (onion-like) shape. However, intermediate forms exist.[4] In nepali onion is called 'pyaj'.
Species that may be confused with A. cepa
Scallions or salad onions may be grown from the Welsh 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.[31]
Hybrids with A. cepa parentage
A number of hybrids are cultivated that have A. cepa parentage, such as the 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.[32]
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.[33] It has been grown for centuries in Japan and China for use as a salad onion.[34]
Under the rules of botanical nomenclature, both the Egyptian onion and Wakegi onion should be combined into one hybrid 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.[2]
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.[33] 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.[35]
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.[36] 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.[36] In this environment, cooking onions have a shelf life of three to four weeks, and sweet onions one to two weeks.[36] Cooking onions will absorb odours from apples and pears.[36] Also, they draw moisture from vegetables they are stored with which may cause them to decay.,[27][36] 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.[36] Sweet onions can also be stored refrigerated; they have a shelf life of approximately one month, optimally uncovered.[36] Irrespective of type, any cut pieces of onion are optimally tightly wrapped, stored away from other produce, and used within two to three days.[36]
Production trends
Top Ten Onions (dry) Producers — 2012(metric tons) |
|
---|---|
![]() |
20,507,759 |
![]() |
13,372,100 |
![]() |
3,320,870 |
![]() |
2,208,080 |
![]() |
1,922,970 |
![]() |
1,900,000 |
![]() |
1,701,100 |
![]() |
1,556,000 |
![]() |
1,536,300 |
![]() |
1,411,650 |
World Total | 74,250,809 |
Source: UN Food & Agriculture Organisation (FAO)[37] |
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 by Sam Seigel and Vincent Kosuga 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 2012.
See also
References
- ^ Germplasm Resources Information Network - (GRIN). "Allium cepa information from NPGS/GRIN". USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?2244. Retrieved 22 April 2011.
- ^ a b c Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. pp. 9–10. ISBN 0-85199-510-1.
- ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 16. ISBN 0-85198-753-2.
- ^ a b c Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. pp. 20–21. ISBN 0-85199-510-1.
- ^ "Allium cepa Linnaeus". Flora of North America. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200027457.
- ^ Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.
- ^ Zohary, Daniel; Hopf, Maria (2000). Domestication of plants in the Old World (Third ed.). Oxford: Oxford University Press. p. 198. ISBN 0-19-850357-1.
- ^ Thompson, Sylvia (1995). The Kitchen Garden. Bantam Books. p. 142.
- ^ a b Thompson, Sylvia (1995). The Kitchen Garden. Bantam Books. p. 143.
- ^ "Genetics Teaching Vignettes: Elementary School". 2004-06-15. http://genetics-education-partnership.mbt.washington.edu/class/elem.htm. Retrieved 2008-01-28.
- ^ "United States Patent Office: Method of coloring eggs or the like". 1925-06-19. http://www.google.com.au/patents?hl=en&lr=&vid=USPAT1538367&id=o2xDAAAAEBAJ&oi=fnd&dq=onion+skin+dye&printsec=abstract#v=onepage&q=onion%20skin%20dye&f=false. Retrieved 2011-09-17.
- ^ a b "Onions Allium cepa". selfsufficientish.com. http://www.selfsufficientish.com/onion.htm. Retrieved 2006-04-02.
- ^ a b c "About Onions: History". http://www.onions-usa.org/about/history.php. Retrieved 2008-01-30.
- ^ a b c R.B. Cope, BSc, BVSc, PhD (August 2005). "Allium species poisoning in dogs and cats". Veterinary Medicine 100 (8): 562–566. ISSN 87507943. http://www2.aspca.org/site/DocServer/vetm0805_562-566.pdf. Retrieved 4 May 2011.
- ^ a b B.S. Salgado; Monteiro, LN; Rocha, NS (2011). "Allium species poisoning in dogs and cats". Journal of Venomous Animals and Toxins Including Tropical Diseases 17 (1): 4–11. doi:10.1590/S1678-91992011000100002. ISSN 16789199.
- ^ a b Sophia Yin, DVM, MS. "Onions: the secret killer?". http://drsophiayin.com/blog/entry/onions_the_secret_killer. Retrieved 4 May 2011.
- ^ Slimestad R, Fossen T, Vågen IM (2007). "Onions: a source of unique dietary flavonoids". J Agric Food Chem 55 (25): 10067–80. PMID 17997520.
- ^ Yang, J.; Meyers, K. J.; Van Der Heide, J.; Liu, R. H. (2004). "Varietal Differences in Phenolic Content and Antioxidant and Antiproliferative Activities of Onions". Journal of Agricultural and Food Chemistry 52 (22): 6787–6793. doi:10.1021/jf0307144. PMID 15506817.
- ^ Chanprapaph, K.; Tanrattanakorn, S.; Wattanakrai, P.; Wongkitisophon, P.; Vachiramon, V. (2012). "Effectiveness of Onion Extract Gel on Surgical Scars in Asians". Dermatology Research and Practice 2012: 1. doi:10.1155/2012/212945. PMC 3423794. PMID 22924037. //www.ncbi.nlm.nih.gov/pmc/articles/PMC3423794/.
- ^ Mikkelson, B (2010-02-26). "Onion Fielded". Snopes.com.
- ^ Simoons, Frederick (1998). Plants of life, plants of death. Univ of Wisconsin Press. p. 568. ISBN 0-299-15904-3. http://books.google.com/?id=KEUAbrBoeBAC&pg=PR11&lpg=PR11&dq=Plants+of+life,+plants+of+death+++bibliography. Retrieved 2009-07-13.
- ^ "The Buddhist Diet". SFSU. http://online.sfsu.edu/~rone/Buddhism/BuddhismAnimalsVegetarian/Buddhist%20Diet.htm.
- ^ Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
- ^ 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. http://www.sciam.com/article.cfm?id=what-is-the-chemical-proc. Retrieved 2007-04-28.
- ^ "FAQ". Onions-usa.org. http://www.onions-usa.org/about/faq.php#cooking. Retrieved 2009-09-04.
- ^ Staunton, Margot (2008-02-01). "Scientists create 'no tears' onions". News.com.au. http://www.news.com.au/story/0,23599,23144566-23109,00.html. Retrieved 2009-09-04.[dead link]
- ^ a b c "Onions: Planting, Growing and Harvesting Onion Plants", Old Farmer's Almanac
- ^ Vegetable Seed Saving Handbook
- ^ "Onion production", USDA
- ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 5. ISBN 0-85198-753-2.
- ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 3. ISBN 0-85198-753-2.
- ^ Germplasm Resources Information Network - (GRIN). "Allium x proliferum information from NPGS/GRIN". USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?404736. Retrieved 21 February 2011.
- ^ a b Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. p. 19. ISBN 0-85199-510-1.
- ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 15. ISBN 0-85198-753-2.
- ^ Friesen, N. & M. Klaas (1998). "Origin of some vegetatively propagated Allium crops studied with RAPD and GISH". Genetic Resources and Crop Evolution 45 (6): 511–523. doi:10.1023/A:1008647700251. http://www.springerlink.com/content/t3520923j4311143/.
- ^ a b c d e f g h Canadian Produce Marketing Association > Home Storage Guide for Fresh Fruits & Vegetables Retrieved August 2010
- ^ "Major Food And Agricultural Commodities And Producers - Countries By Commodity". Fao.org. http://faostat.fao.org/site/567/DesktopDefault.aspx?PageID=567#ancor. Retrieved 2012-05-18.
Further reading
- Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry (UK). ISBN 978-0-85404-190-9.
- Sen, Colleen T. (2004). Food culture in India. Greenwood Publishing. ISBN 0-313-32487-5.
- Barbagallo, Tricia (June 1, 2005). "Black Beach: The Mucklands of Canastota, New York" (PDF). http://www.archives.nysed.gov/apt/magazine/MagSummer05FeatureArticle_000.pdf. Retrieved 2008-06-04.
External links
- PROTAbase on Allium cepa
- Allium cepa L. Medicinal Plant Images Database (School of Chinese Medicine, Hong Kong Baptist University) (traditional Chinese)(English)