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[[File:Gluten Sources.png|right|thumb|upright=1.30|Sources of gluten. Clockwise from top: High-gluten [[wheat flour]], European [[spelt]], [[barley]], rolled [[rye flakes]].]]

'''Gluten''' (from Latin ''[[:wikt:gluten|gluten]]'', "[[glue]]") is a [[protein]] composite found in [[wheat]] and related grains, including [[barley]] and [[rye]]. Gluten gives [[viscoelasticity|elasticity]] to [[dough]], helping it [[leavening agent|rise]] and keep its shape and often gives the final product a [[chewiness|chewy]] texture. Gluten is used in cosmetics, hair products, and other dermatological preparations.<ref>{{cite web|url=http://thechart.blogs.cnn.com/2011/10/31/gluten-in-cosmetics-may-pose-hidden-threat-to-celiac-patients/|title=Gluten in cosmetics may pose hidden threat to celiac patients|last=Harding|first=Anne|date=31 October 2011|publisher=CNN Health|accessdate=21 October 2012}}</ref>

Gluten is the composite of a ''[[gliadin]]'' and a ''[[glutenin]]'', which is conjoined with [[starch]] in the [[endosperm]] of various [[Triticeae glutens|grass-related]] [[cereal|grains]]. The [[prolamin]] and glutelin from wheat (gliadin, which is alcohol-soluble, and [[glutenin]], which is only soluble in dilute acids or alkalis) constitute about 80% of the protein contained in wheat [[fruit]]. Being [[Solubility|insoluble]] in water, they can be purified by washing away the associated starch. Worldwide, gluten is a source of protein, both in foods prepared directly from sources containing it, and as an [[food additive|additive]] to [[Low-protein diet|foods otherwise low in protein]].

The fruit of most [[flowering plant]]s have endosperms with stored protein to nourish [[Plant embryogenesis|embryonic plants]] during [[germination]]. True gluten, with gliadin and glutenin, is limited to certain members of the [[Poaceae|grass]] family. The stored proteins of [[maize]] and [[rice]] are sometimes called glutens, but their proteins differ from true gluten.

About 1 in 133 people in developed nations have intolerance to gluten.<ref>{{cite news |newspaper= Journal Sentinel |location= Milwaukee |url= http://www.jsonline.com/features/food/92134239.html |title=Gluten intolerance rising in developed countries |date=27 June 2010 |accessdate=5 July 2013}}</ref> [[Gluten sensitivity]] is classified as intolerance, not an [[allergy]].

== Extraction ==
Gluten is extracted from [[flour]] by kneading the flour, agglomerating the gluten into an elastic network, a [[dough]], and then washing out the [[starch]]. Starch granules [[suspension (chemistry)|disperse]] in cold/low temperature water, and the dispersed starch will be [[sedimentation|sedimented]] and dried.<ref>{{cite web|url=http://chaos-its-not-just-a-theory.com/2010/06/20/extracting-gluten-from-flour/|title=Extracting Gluten from Flour|date=20 June 2010|publisher=Chaos – it's not just a theory…|accessdate=21 October 2012}}</ref> If a [[salt|saline]] solution is used instead of water, a purer protein is obtained, with certain harmless [[impurity|impurities]] going into the solution with the starch. Where starch is the prime product, cold water is the favored solvent because the impurities stay with the gluten.

In home or restaurant cooking, a ball of wheat flour dough is kneaded under water until the starch disperses out. In industrial production, a [[slurry]] of wheat flour is kneaded vigorously by machinery until the gluten agglomerates into a mass. This mass is collected by [[centrifugation]], then transported through several stages integrated in a continuous process.<ref>{{cite web
   | url=http://www.westfalia-separator.com/applications/renewable-resources/wheat-starch-wheat-gluten.html
   | title=Wheat Starch and Wheat Gluten
   | publisher=GEA Westfalia Separator Group
   | accessdate=19 October 2011}}
</ref>
Approximately 65% of the water in the wet gluten is removed by means of a [[screw press]]; the remainder is sprayed through an [[atomizer nozzle]] into a [[drying]] chamber, where it remains at an elevated temperature a short time to evaporate the water without denaturing the gluten. The process yields a flour-like powder with a 7% moisture content, which is [[Air cooling|air cooled]] and [[Pneumatics|pneumatically]] transported to a receiving vessel. In the final step, the collected gluten is [[Sieve|sifted]] and [[Mill (grinding)|milled]] to produce a uniform product.<ref>{{cite web
   | url=http://www.barr-rosin.com/applications/wheat.asp
   | title=Wheat |publisher=GEA Barr-Rosin
   | accessdate=8 September 2009}}</ref>

== Uses ==
[[File:Wheat field.jpg|thumb|[[Wheat]], a prime source of gluten]]

===Bread products===
Gluten forms when glutenin [[molecule]]s cross-link to form a sub-microscopic network attached to gliadin, which contributes [[viscosity]] (thickness) and extensibility to the mix.<ref>
  {{cite web | last1=Woychick | first1=JH | author2=et al.
  | url=http://www.friedli.com/research/PhD/gluten/chap2.html
  | title=The Gluten Proteins and Deamidated Soluble Wheat Protein
  | accessdate=8 September 2009}}
</ref> If this dough is [[Leavening agent|leavened]] with [[yeast]], [[fermentation (food)|fermentation]] produces [[carbon dioxide]] bubbles, which, trapped by the gluten network, cause the dough to rise. [[Baking]] [[denaturation (biochemistry)|coagulates]] the gluten, which, along with starch, stabilizes the shape of the final product. Gluten content has been implicated as a factor in the [[staling]] of bread, possibly because it binds water through hydration.<ref>
   Sahlstrom, S. & Brathen, E. (1997). "Effects of enzyme
   preparations for baking, mixing time and resting time on
   bread quality and bread staling". ''Food Chemistry'', 58, 1,
   75-80. Effects of wheat variety and processing conditions
   in experimental bread-baking studied by univariate and
   [[multivariate analysis]].</ref>

The development of gluten (i.e., enhancing its elasticity) affects the texture of the baked goods. Gluten's attainable elasticity is proportional to its content of glutenins with low molecular weights as this portion contains the preponderance of the sulfur atoms responsible for the cross-linking in the network.<ref>{{cite journal
 | last = Edwards | first = N. M.
 | coauthors = Mulvaney, S. J.; Scanlon, M. G.; Dexter, J. E.
 | year = 2003
 | title =  Role of gluten and its components in determining durum semolina dough viscoelastic properties
 | journal=Cereal chemistry | volume=80 | issue=6 | pages=755–763
 | url = http://cat.inist.fr/?aModele=afficheN&cpsidt=15273405
 | accessdate = 2007-08-14 | doi =  10.1094/CCHEM.2003.80.6.755
}}</ref><ref>{{cite journal
 | last = Tosi | first = Paola
 | coauthors = Masci, Stefania; Giovangrossi, Angela2; D'Ovidio, Renato; Bekes, Frank; Larroque, Oscar; Napier, Johnathan;  Shewry, Peter
 |date=September 2005
 | title =  Modification of the Low Molecular Weight (LMW) Glutenin Composition of Transgenic Durum Wheat: Effects on  Glutenin Polymer Size and Gluten Functionality
 | journal=Molecular Breeding | volume=16 | issue=2 | pages=113–126
 | url = http://www.ingentaconnect.com/content/klu/molb/2005/00000016/00000002/00005912
 | accessdate = 2007-08-14 | doi =  10.1007/s11032-005-5912-1
}}</ref>
More refining (of the gluten) leads to chewier products such as [[pizza]] and [[bagel]]s, while less refining yields tender baked goods such as [[pastry]] products.<ref name="Baking Technology, Bread">{{cite web
 | url = http://www.bakersassist.nl/processing5-2.htm
 | title = Baking Technology, Bread | publisher = Bakersassist
 | accessdate = 2007-08-14}}</ref>

Generally, [[bread]] [[flour]]s are high in gluten (hard wheat); pastry flours have a lower gluten content. [[Kneading]] promotes the formation of gluten strands and cross-links, creating baked products that are chewier in proportion to the length of kneading. An increased moisture content in the dough enhances gluten development,<ref name="Baking Technology, Bread"/> and very wet doughs left to rise for a long time require no kneading (see [[no-knead bread]]). [[Shortening]] inhibits formation of cross-links and is used, along with diminished water and less kneading, when a tender and flaky product, such as a pie crust, is desired.

The strength and elasticity of gluten in flour is measured in the baking industry using a [[farinograph]]. This gives the baker a measurement of quality for different varieties of flours in developing recipes for various baked goods.{{citation needed|date=December 2013}}

====Added gluten====
Gluten, when dried and milled to a powder and added to ordinary flour dough, improves a dough's ability to rise and increases the bread's structural stability and chewiness.<ref>{{cite book|authors=   Amendola, J.; Rees, N.; & Lundberg, D. E. |year=2002|title=Understanding Baking}}</ref> Gluten-added dough must be worked vigorously to induce it to rise to its full capacity; an automatic [[bread machine]] or [[food processor]] may be required for kneading.<ref>{{cite book|authors=Eckhardt, L.W. & Butts, D.C. |year=1997|title=Rustic European Breads from your Bread Machine}}</ref> The added gluten provides supplemental protein to products with low or nonexistent protein levels.{{citation needed|date=December 2013}}

===Imitation meats===
[[File:Wheat gluten (vegetarian mock duck) 2007.jpg|thumb|Gluten is often used in imitation meats (such as this mock "duck") to provide supplemental protein and variety in vegetarian diets.]]
{{Details|Wheat gluten (food)|the use of gluten in cooking}}
Gluten, especially [[wheat gluten (food)|wheat gluten]], is often the basis for [[Meat analogue|imitation meats]] resembling [[beef]], [[Chicken (food)|chicken]], [[Duck (food)|duck]] (see [[mock duck]]), [[Fish (food)|fish]], and [[pork]]. When cooked in [[broth]], gluten absorbs some of the surrounding liquid (including the taste) and becomes firm to the bite.{{citation needed|date=December 2013}}

=== Added to other foods ===
Gluten is often present in [[beer]] and [[soy sauce]], and can be used as a [[food additive|stabilizing agent]] in more unexpected food products, such as [[ice cream]] and [[ketchup]].<ref>{{cite web|url=http://spiritfoods.net/what-does-gluten-free-mean/|title=What Does Gluten-Free Mean?|publisher=Spiritfoods|accessdate=21 October 2012}}</ref><ref>{{cite web
  | url=http://bidmc.harvard.edu/default.asp?leaf_id=12799
  | title=Following a Gluten-free Diet
  | publisher=Beth Israel Deaconess Medical Center
  | author=A Harvard teaching hospital}}
{{Dead link|date=May 2012}}</ref> Foods of this kind raise a problem, because the hidden gluten constitutes a hazard for people with [[Coeliac disease|celiac disease]].

===Animal feed===
The protein content of some [[pet food]]s may also be enhanced by adding gluten.<ref>{{cite web
  | title = Pet Foods   | accessdate = 14 August 2007
  | publisher = International Wheat Gluten Association
  | archiveurl = http://web.archive.org/web/20071007175039/http://www.iwga.net/04_pet.htm <!-- Bot retrieved archive -->
  | archivedate = 2007-10-07| url = http://www.iwga.net/04_pet.htm <!-- Bot retrieved archive -->}}</ref>

== Adverse reactions ==
{{Main|Gluten-sensitive enteropathy-associated conditions|Gluten-sensitive idiopathic neuropathies}}
Gluten is known to cause adverse health issues ranging from bloating, gas, diarrhea and vomiting to migraine headaches and joint pain in those who suffer from [[gluten sensitivity]], primarily as a result of [[coeliac disease]] (spelled "celiac" in American English) and including non-celiac gluten sensitivity and wheat allergy.

Celiac disease is an inherited autoimmune disorder that affects the digestive process of the small intestine.

Non-celiac gluten sensitivity, (what many call “gluten intolerance”) causes the body to mount a stress response (often GI symptoms) different from the immunological response that occurs in those who have celiac disease (which most often causes intestinal tissue damage).

As with most allergies, a wheat allergy causes the immune system to respond to a food protein because it considers it dangerous to the body when it actually isn’t. This immune response is often time-limited and does not cause lasting harm to body tissues.

<ref>http://www.cureceliacdisease.org/archives/faq/what-is-the-difference-between-gluten-intolerance-gluten-sensitivity-and-wheat-allergy</ref>

In 2009 research showed between 0.5 and 1.0 percent of people in the US and UK are sensitive to gluten due to coeliac disease.<ref name = "NIH">{{cite web
  | url= http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/index.htm
  | title=Celiac Disease
  | work=National Digestive Diseases Information Clearing House
  | publisher=National Institutes of Health (NIH)
  | year=2004 | accessdate=8 September 2009}}
</ref><ref>{{cite web
  | url = http://www.guideline.gov/summary/summary.aspx?doc_id=5692&nbr=0
  | title = Celiac disease
  | publisher = National Institutes of Health (NIH)
  | work = Consensus Development Panel on Celiac Disease
  | year = 2005 | accessdate = 2007-08-14}}
</ref><ref>{{cite web
  |title=Coeliac Disease|url=http://www.coeliac.org.uk/coeliac-disease/what-is-coeliac-disease
  |work=What is coeliac disease?
  |publisher=Coeliac UK
  |accessdate=18 April 2013}}
</ref> It probably occurs with comparable frequencies among all wheat-eating populations in the world.<ref name=VanHeelWest>{{cite journal | author = van Heel D, West J | title = Recent advances in coeliac disease | url = http://gut.bmjjournals.com/cgi/content/full/55/7/1037 | journal = Gut | volume = 55 | issue = 7 | pages = 1037–46 | year = 2006 | pmid = 16766754 | doi = 10.1136/gut.2005.075119 | pmc = 1856316}}</ref> Coeliac disease has no cure but is manageable with a [[gluten-free diet]]. [[Wheat allergy]] and celiac disease are different disorders.<ref>{{cite web |url=http://www.food.gov.uk/multimedia/pdfs/allergyfactsheettwo.pdf |title=Food intolerance and coeliac disease |publisher=Food Standards Agency |date=September 2006 |format=PDF |accessdate=8 September 2009}}</ref>
<!-- EDITORIAL note: The important subject of wheat-protein related disorders is mentioned only briefly here because a series of articles about Gluten sensitivity in Wikipedia thoroughly discusses the diverse pathologies associated with wheat consumption. -->

==Labeling==

===International Labeling Standards===
The ''[[Codex Alimentarius]]'' [[international standard]]s for [[food labelling|food labeling]] has a standard relating to the labeling of products as "gluten-free". It only applies to foods that would normally contain gluten.<ref>{{cite web|url=http://www.codexalimentarius.org/download/standards/291/cxs_118e.pdf|publisher=[[Codex Alimentarius]]|title=Codex Standard For "Gluten-Free Foods" CODEX STAN 118-1981|date=February 22, 2006|format=PDF}}</ref>

===Labeling in Canada===
Labels for all food products sold in Canada must clearly identify the presence of gluten if it is present at a level greater than 10 ppm.<ref>[http://www.celiac.ca/index.php/about-celiac-disease/food-labelling/ Canadian Celiac Association]</ref>

===Labeling in the UK===
In the United Kingdom, only cereals must be labelled;  labelling of other products is voluntary.<ref>{{cite web
  |url= http://www.food.gov.uk/multimedia/pdfs/labelamendguid21nov05.pdf
  |date=November 2005
  | title=Guidance Notes on the Food Labelling (Amendment) (No. 2) Regulations 2004
  | publisher=[[Food Standards Agency]] |format=PDF}}</ref>

===Labeling in the US===
In the United States, gluten might not be listed on labels, because the [[US Food and Drug Administration]] (FDA) has historically classified gluten as GRAS ("[[generally recognized as safe]]"). In August 2013, FDA issued a final rule to define the term “gluten-free” for voluntary use in the labeling of foods i.e. "presence of gluten in the food must be less than 20 ppm."<ref>http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Allergens/ucm362880.htm</ref>

== References ==

=== Citations ===
{{Reflist|2}}

=== Bibliography ===
* {{Cite web
|last1 = Curtis |first1 = B.C. |last2 = Rajaram |first2 = S. |last3 = Macpherson |first3 = H.G.
|title = Bread Wheat, Improvement and production — FAO Plant Production and Protection Series No. #30. |url = http://www.fao.org/DOCREP/006/Y4011E/y4011e05.htm |accessdate = 2007-08-21
|postscript = <!--None-->
}}
* {{Cite web |last = Pfluger |first = Laura
|title = Marker Assisted Selection in Wheat, ''Quality traits. Gluten Strength'', Coordinated Agricultural Project (funded by USDACREES) |url = http://maswheat.ucdavis.edu/protocols/gluten/index.htm |accessdate = 2007-09-29 |postscript = <!--None-->
}}
* {{Cite journal |publisher = USDA Cereal Disease Laboratory
|title = Agricultural Databases, Statistics, etc. |url = http://www.ars.usda.gov/Main/docs.htm?docid = 11017|accessdate  = 2007-08-21 |postscript = <!--None-->
}}
* {{Cite journal |last = Wieser |first = H.
|title = Cereal Chemistry and Dough Properties, KL1-''Gluten Chemistry''
|publisher = German Research Centre of Food Chemistry and Cereal Chemistry and Hans-Dieter-Belitz-Institute for Cereal Grain Research, D-85748 Garching, Germany
|year = 2007 |url = http://fp.cerealsandeurope.net/events/sourdough/session1.htm |accessdate = 2007-09-27 |postscript = <!--None-->
}}
* {{Cite book |last1 = Wrigley |first1 = C.W |last2 = Bekes |first2 = F. |last3 = Bushuk |first3 = W
|title = The Gluten Composition of Wheat Varieties and Genotypes
|publisher = AACC International |year = 2006 |url = http://aaccnet.org/grainbin/gluten_gliadin.asp |isbn = 1-891127-51-9 |accessdate = 2007-09-21 |postscript = <!--None-->
}}



[[Category:Nutrition]]