gluten

1. The mixture of proteins, including gliadins and glutelins, found in wheat grains, which are not soluble in water and which give wheat dough its elastic texture.
2. Any of the prolamins found in cereal grains, especially the prolamins in wheat, rye, barley, and possibly oats, that cause digestive disorders such as celiac disease.

[French, from Latin glūten, glue.]

The term ‘gluten’ comes from the Latin word for glue. The use of the word gluten to describe a sticky proteinatious component of dough was established by the middle of the nineteenth century. Mrs Beeton in her famous Book of household management observed that when flour and water were mixed and kneaded, an elastic dough was produced which was best using wheat flour, less satisfactory with rye flour, and inadequate with barley, maize (corn), oats, or rice. This sticky elastic substance, or gluten, is essential for making satisfactory leavened bread. Bubbles of carbon dioxide released from fermenting yeast are trapped by the visco-elastic protein, ensuring a light honeycombed texture for the dough. The elastic nature of gluten also holds particles of the dough together, preventing crumbling during rolling and shaping.

Wheat gluten can be extracted from wheat flour by adding sufficient water to make a kneadable dough which is then washed with a stream of cold water. The water-soluble protein and starch granules are thus flushed away, leaving a sticky mass high in structural plant protein. About 70% of the mass is water and 30% is protein. With drying, a pale, yellow-grey powder is produced. Gluten is poorly soluble in water, but the fraction known as ‘gliadin’ is soluble in aqueous alcohol. Two thirds of gluten protein is in the form of glutenins, which are insoluble in ethyl alcohol but soluble in a mixture of ethanoic acid, urea, and cetrimide. There are more than 40 different gliadin proteins, which traditionally have been separated by starch gel electrophoresis. The fraction with the fastest mobility is known as alpha gliadin, with progressively slower mobility groups classified as beta, gamma, and omega. These proteins have molecular weights between 30 000 and 40 000. The glutenin proteins are much larger units, mostly around 2 000 000 molecular weight. The glutenin protein chains form a three-dimensional net when hydrated (mixed with water) and this gives the elastic properties to gluten.

Not all sticky plant cereals in our diet contain gluten. A type of rice grown in the Far East known as glutinous or sticky rice contains no proteinatious gluten and owes its sticky nature to a waxy carbohydrate.

The sticky nature of gluten has been utilized as a paper and fabric glue, as in making papier-mâché and wallpaper paste. Wheat gluten has also been used as a cattle feed and as a starting point for the manufacture of the food flavour enhancer, monosodium glutamate.

Although the presence of gluten in wheat flour has been utilized to create a variety of pasta shapes, such as noodles, spaghetti, and tagliatelle, gluten is not an essential human nutrient. There is however, some experimental work to suggest that dietary gluten may be protective against some toxic substances. For example, gluten in the diet of rats reduces the liver toxicity of a known toxic chemical, D-galactosamine.

Gluten and coeliac disease

The importance of gluten in the human diet however, relates to the fact that 1 in 200-300 of the European Caucasian population are intolerant to wheat, barley, and rye gluten.

The lining cells of the small intestine become damaged and the patients develop a condition known as coeliac disease or permanent gluten-induced enteropathy. The classical presentation was of a pre-school child with diarrhoea and weight loss. Possibly due to nutritional campaigns to delay the introduction of gluten to infant diets, an insidious onset later in childhood, with anaemia and poor growth in height, is now more frequently seen. Onset in adult life may occur, with anaemia, infertility, and vitamin D deficient bone disease amongst the possible presenting features, although gastrointestinal symptoms and weight loss may, as in children, be the main complaints.

Although this medical condition was described in the first century ad by Aretaeus and accurately, clinically, delineated by a London physician, Dr Samuel Gee, in the late nineteenth century, its cause and cure were not discovered until the 1940s. Dr W. K. Dicke, an astute Dutch physician, noticed that in Holland children with coeliac disease were temporarily cured and improved in health during the World War II famine created by Nazi occupation. He then observed the relapse in their condition when wheat flour was flown in by the Swedish authorities. Subsequent work by Dicke and colleagues and later investigators identified the toxic factor to be an oligopeptide in alpha gliadin.

The practice of cereal cultivation by man started first in the Middle East around 8000 years bc. There was subsequently a gradual spread north and westward. Cereal cultivation arrived late in southwest Ireland, at around 3000 years bc, and wheat was not a staple food until after the potato famine of 1847. The majority of patients suffering from gluten-induced enteropathy (coeliac disease) are of tissue type HLA B8. The incidence of coeliac disease in southwest Ireland, particularly Galway, is amongst the highest in Europe, and there is correspondingly a high prevalence of HLA B8 tissue type. It has been suggested that when populations consume large quantities of gluten from wheat cereals the susceptible HLA B8 individuals develop disease and are at a reproductive disadvantage compared with those not genetically predisposed to the disease, leading to a reduced proportion of B8 individuals in subsequent generations.

Many commercially-prepared foods in Europe contain gluten. Wheat flour is added as a bulking agent in many items of confectionery, as thickeners in sauces, to give bulk and to reduce the cost of meat products, such as sausage meat, and even in some pharmaceutical preparations. It is therefore difficult without a detailed knowledge of the constituents of manufactured foods for an individual to adhere strictly to a gluten free diet. Some food labels indicate the product is gluten free, either in words or as a symbol — an ear of wheat with a cross through it. ‘Gluten free’ flour and bread are available and usually contain starch from maize (corn) or rice, with some of the elastic properties of gluten being provided by guar gum or similar substances.

— T. J. Evans

See also alimentary system; diets.

The protein complex in wheat, and to a lesser extent barley and rye, which gives dough the viscid property that holds gas when it rises. It is a mixture of two proteins, gliadin and glutelin. Allergy to, or intolerance of, the gliadin fraction of gluten is coeliac disease.

In the undamaged state with extensible properties it is termed vital gluten; when overheated, these properties are lost and the product, devitalized gluten, is used for protein enrichment of foods. See also food, gluten-free.

A mixture of two proteins, gliadin and glutenin, gluten is a major component of rye, wheat flower and barley, imparting springiness into wheat products. Gluten is not present in oats or maize. See also coeliac disease.

[GLOO-tihn] Wheat and other cereals that are made into flour contain proteins, one of which is glutenin, commonly known as gluten. Viewed alone, gluten is a tough, elastic, grayish substance resembling chewing gum. It's the gluten in flour that, when a dough is kneaded, helps hold in the gas bubbles formed by the leavening agent (see leavener). Gas contained within a dough or batter helps a bread or other baked good rise, creating a light structure. Most (but not all) flours contain gluten in varying amounts. Bread (or hard wheat) flour has a high gluten content and is therefore good for yeast breads, which require an elastic framework. On the other hand, low-protein (and therefore low-gluten) cake flour has a softer, less elastic quality and is better suited for cakes. See also bread; flour; seitan.

An insoluble protein constituent of wheat and other grains consisting of a mixture of gliadin, glutenin, and other proteins. Gluten provides the elastic qualities of bread dough.

For more information on gluten, visit Britannica.com.

The protein of wheat and other grains that gives dough its tough, elastic character.

• g. sensitivity — called also gluten enteropathy. See wheat-sensitive enteropathy.

Tutor's tip: You can be a "glutton" (a heavy eater) for breads and cereals that have a lot of "gluten" (proteins found in cereal grains) in them.

For the food products made from gluten see Wheat gluten (food).

Wheat seed, sectioned to reveal endosperm and embryo

Wheat, a prime source of gluten

Gluten is a composite of the proteins gliadin and glutenin. These exist, conjoined with starch, in the endosperms of some grass-related grains, notably wheat, rye, and barley. Gliadin and glutenin comprise about 80% of the protein contained in wheat seed. Being insoluble in water, they can be purified by washing away the associated starch. Worldwide, gluten is an important source of nutritional protein, both in foods prepared directly from sources containing it, and as an additive to foods otherwise low in protein.^{[citation needed]}

The seeds of most flowering plants have endosperms with stored protein to nourish embryonic plants during germination, but true gluten, with gliadin and glutenin, is limited to certain members of the grass family. The stored proteins of maize and rice are sometimes called glutens, but their proteins differ from wheat gluten by lacking gliadin. The glutenin in wheat flour gives kneaded dough its elasticity, allows leavening and contributes chewiness to baked products like bagels.

Although wheat supplies much of the world's dietary protein and food supply, as much as 0.5% to 1% of the population of the United States has celiac disease, a condition which results from an adverse immune system response to gluten.^[1][2] The manifestations of celiac disease range from no symptoms to malabsorption of nutrients with involvement of multiple organ systems. The only effective treatment is a lifelong gluten-free diet.

Contents 1 Extraction 2 Uses 2.1 Gluten as an additive 3 Adverse reactions 4 See also 5 References 6 Further reading

Extraction

While there is no evidence of this, legend attributes the discovery of gluten to Buddhist monks in 7th century China who sought meat-like ingredients for use in their vegetarian diet. With easily available wheat flour and water they made a dough which they submerged in cold water and kneaded. The water dissolved the starchy components of the dough and left behind an insoluble, gummy mass, 70% to 80% of which was gluten.

Gluten is still extracted from flour by washing out the starch by means not fundamentally different from the ancient way; this exploited the fact that starch is water-soluble while gluten is not, and also that gluten binds together strongly, while starch dissolved in cold water is mobile. If a saline solution is used instead of water a purer protein is obtained, with certain harmless impurities going into solution with the starch. However, on an industrial scale, starch is the prime product, so cold water is the favored solvent. To effect the separation, a slurry of wheat flour is stirred vigorously by machinery until the starch dissolves and the gluten consolidates into a mass, which is collected by centrifugation, then carried, by complex machinery,^[3] through several stages combined into a continuous process: Approximately 65% of the water in the wet gluten is removed by means of a screw press, and the residue is sprayed through an atomizing nozzle into a drying chamber, where it remains at an elevated temperature only long enough to evaporate the water without denaturing the gluten. This yields a flour-like powder with a 7% moisture content, which is quickly air-cooled and pneumatically transported to a receiving vessel. In the final step, the collected gluten is sifted and milled to make the product uniform.^[4]

Uses

When dough made with wheat flour is kneaded, gluten forms when glutenin molecules cross-link to make a sub-microscopic network and associates with gliadin, which contributes viscosity and extensibility to the mix.^[5] If such dough is leavened with yeast, sugar fermentation produces bubbles of carbon dioxide which, trapped by the gluten network, cause the dough to swell or rise. Baking 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 by hydration.^[6]

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 because that fraction contains the preponderance of the sulfur atoms responsible for the cross-linking in the network.^[7][8] More development leads to chewier products like pizza and bagels, while less development yields tender baked goods. In general, bread flours are high in gluten while cake flours are low. Kneading promotes the formation of gluten strands and cross-links, so a baked product is chewier in proportion to how much the dough is worked. Increased wetness of the dough also enhances gluten development.^[9] Shortening inhibits formation of cross-links, so it is used, along with diminished water and minimal working, when a tender and flaky product, such as pie crust, is desired.

Gluten, dried and milled to powder and added to ordinary flour dough, improves rising and increases the bread's structural stability and chewiness,^[10]. Such doughs must be worked vigorously if they are to rise to their full capacity, so a bread machine or food processor may be required for their kneading.^[11] The added gluten provides supplemental protein to what would otherwise be high-carbohydrate preparations. The protein content of pet foods is also enhanced by adding gluten.^[12] When cooked in broth, gluten absorbs some of the surrounding liquid (including the taste) and becomes firm to the bite, so is widely used in vegetarian, vegan and Buddhist cuisines as a meat substitute. In China, as miàn jin, it is the basis for imitation meats resembling chicken, duck, fish, pork and beef. The Japanese variants, called namafu, yakifu, and seitan, are used in the same way.

Gluten as an additive

The "Codex Alimentarius" set of international standards for food labeling has a standard relating to the labelling of products as "gluten free", however this standard does not apply to "foods which in their normal form do not contain gluten".^[13] Gluten is used as a stabilizing agent in products like ice-cream and ketchup, where it may be unexpected.^[14][15] Foods of this kind present a problem because the hidden gluten constitutes a hazard for people with celiac disease: In the United States, at least, gluten may not be listed on the labels of such foods because the U.S, Food and Drug Administration has classified gluten as GRAS (Generally recognized as safe).^[16] Requirements for proper labeling are being formulated by the USDA. In the United Kingdom, only cereals currently need to be labelled, while other products are voluntary.^[17] In fact, in the UK most gluten free food is clearly labelled so, as is non-gluten-free food.

Adverse reactions

Main articles: Gluten sensitivity and Gluten-free diet

Between 0.5 and 1.0 percent of people in the United States are sensitive to gluten due to celiac disease.^[18][19] Celiac disease is caused by an abnormal immune reaction to partially digested gliadin. It probably occurs with comparable frequencies among all wheat-eating populations in the world.^[20] Certain allergies and neuropathies are also caused by gluten consumption and inhalation.^[21]

Note that wheat allergy and celiac disease are different disorders.^[22]

See also

• Textured vegetable protein
• Zein
• Triticeae glutens

References

1. ^ Presutti, John; et al. (2007-12-27). "Celiac Disease". American Family Physician 76 (12): 196–1802. http://www.aafp.org/afp/20071215/1795.html. 
2. ^ Hill, ID; Horvath; Fasano (Jan 1995). "Epidemiology of celiac disease". The American journal of gastroenterology 90 (1): 163–4. ISSN 0002-9270. PMID 7801932.  edit
3. ^ "Starch Technology & Industrial Biotechnology". Westfalia Separator Industry. http://www.westfalia-separator.com/en/comp/comp_industry_starch.php. Retrieved 2007-08-14. 
4. ^ "Wheat". GEA Barr-Rosin. http://www.barr-rosin.com/applications/wheat.asp. Retrieved 8 September 2009. 
5. ^ Woychick, JH. "The Gluten Proteins and Deamidated Soluble Wheat Protein (SWP)". http://www.friedli.com/research/PhD/gluten/chap2.html. Retrieved 8 September 2009. 
6. ^ 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 analyses.
7. ^ Edwards, N. M.; Mulvaney, S. J.; Scanlon, M. G.; Dexter, J. E. (2003). "Role of gluten and its components in determining durum semolina dough viscoelastic properties". Cereal chemistry 80 (6): 755–763. doi:10.1094/CCHEM.2003.80.6.755. http://cat.inist.fr/?aModele=afficheN&cpsidt=15273405. Retrieved 2007-08-14. 
8. ^ Tosi, Paola; Masci, Stefania; Giovangrossi, Angela2; D'Ovidio, Renato; Bekes, Frank; Larroque, Oscar; Napier, Johnathan; Shewry, Peter (September 2005). "[http://www.ingentaconnect.com/content/klu/molb/2005/00000016/00000002/00005912 Modification of the Low Molecular Weight (LMW) Glutenin Composition of Transgenic Durum Wheat: Effects on Glutenin Polymer Size and Gluten Functionality]". Molecular Breeding 16 (2): 113–126. doi:10.1007/s11032-005-5912-1. http://www.ingentaconnect.com/content/klu/molb/2005/00000016/00000002/00005912. Retrieved 2007-08-14. 
9. ^ "Baking Technology, Bread". Bakersassist. http://www.bakersassist.nl/processing5-2.htm. Retrieved 2007-08-14. 
10. ^ Amendola, J., Rees, N., & Lundberg, D. E. (2002). Understanding Baking
11. ^ Echkardt, LW & Butts, DC. (1997). Rustic European Breads from your Bread Machine
12. ^ "Pet Foods". International Wheat Gluten Association. http://www.iwga.net/04_pet.htm. Retrieved 2007-08-14. 
13. ^ "Codex Standard For "Gluten-Free Foods" CODEX STAN 118-1981" (PDF). Codex Alimentarius. February 22, 2006. http://www.codexalimentarius.net/download/standards/291/CXS_118e.pdf. 
14. ^ Pat Kendall, Ph.D., R.D. (March 31, 2003). "Gluten sensitivity more widespread than previously thought". Colorado State University Extension. http://www.ext.colostate.edu/pubs/columnnn/nn030331.html. 
15. ^ "Following a Gluten-free Diet". Beth Israel Deaconess Medical Center. A Harvard teaching hospital. http://bidmc.harvard.edu/default.asp?leaf_id=12799. 
16. ^ "Sec. 184.1322 Wheat gluten". Code of Federal Regulations Center. April 1, 2007. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=184.1322. 
17. ^ "Guidance Notes on the Food Labelling (Amendment) (No. 2) Regulations 2004" (PDF). Food Standards Agency. November 2005. http://www.food.gov.uk/multimedia/pdfs/labelamendguid21nov05.pdf. 
18. ^ "Celiac Disease". National Digestive Diseases Information Clearing House. National Institutes of Health (NIH). 2004. http://digestive.niddk.nih.gov/ddiseases/pubs/celiac/index.htm. Retrieved 8 September 2009. 
19. ^ "Celiac disease". Consensus Development Panel on Celiac Disease. National Institutes of Health (NIH). 2005. http://www.guideline.gov/summary/summary.aspx?doc_id=5692&nbr=0. Retrieved 2007-08-14. 
20. ^ van Heel D, West J (2006). "Recent advances in coeliac disease". Gut 55 (7): 1037–46. doi:10.1136/gut.2005.075119. PMID 16766754. http://gut.bmjjournals.com/cgi/content/full/55/7/1037. 
21. ^ David A. Nelsen. "Gluten Sensitive Enteropathy". http://www.uams.edu/celiac/review/GSE1.htm. Retrieved 2007-08-14. 
22. ^ "Food intolerance and coeliac disease" (PDF). Food Standards Agency. September 2006. http://www.food.gov.uk/multimedia/pdfs/allergyfactsheettwo.pdf. Retrieved 8 September 2009. 

Further reading

• Curtis, B.C.; Rajaram, S.; Macpherson, H.G., Bread Wheat, Improvement and production — FAO Plant Production and Protection Series No. #30., http://www.fao.org/DOCREP/006/Y4011E/y4011e05.htm, retrieved 2007-08-21 
• Pfluger, Laura, Marker Assisted Selection in Wheat, Quality traits. Gluten Strength, Coordinated Agricultural Project (funded by USDACREES), http://maswheat.ucdavis.edu/protocols/gluten/index.htm, retrieved 2007-09-29 
• Agricultural Databases, Statistics, etc., USDA Cereal Disease Laboratory, http://www.ars.usda.gov/Main/docs.htm?docid=11017 
• Wieser, H. (2007), Cereal Chemistry and Dough Properties, KL1-Gluten Chemistry, German Research Centre of Food Chemistry and Cereal Chemistry and Hans-Dieter-Belitz-Institute for Cereal Grain Research, D-85748 Garching, Germany, http://fp.cerealsandeurope.net/events/sourdough/session1.htm, retrieved 2007-09-27 
• Wrigley, C.W; Bekes, F.; Bushuk, W (2006), The Gluten Composition of Wheat Varieties and Genotypes, AACC International, ISBN 1-891127-51-9, http://aaccnet.org/grainbin/gluten_gliadin.asp, retrieved 2007-09-21 

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Dansk (Danish)
n. - gluten

Nederlands (Dutch)
gluten, kleverige stof

Français (French)
n. - gluten

Deutsch (German)
n. - (chem.) Gluten, Kleber, Leim

Ελληνική (Greek)
n. - (βιολ.) γλουτένη, γλοιίνη

Italiano (Italian)
glutine

Português (Portuguese)
n. - glúten (m)

Русский (Russian)
клейковина

Español (Spanish)
n. - gluten

Svenska (Swedish)
n. - gluten

中文（简体）(Chinese (Simplified))
麸质

中文（繁體）(Chinese (Traditional))
n. - 麩質

한국어 (Korean)
n. - (단백질의 일종) 글루텐

日本語 (Japanese)
n. - グルテン

العربيه (Arabic)
‏(الاسم) غراء, مادة بروتينيه دبقه‏

עברית (Hebrew)
n. - ‮תרכובת שני חלבונים הנמצאת בקמח חיטה, חומר דביק‬

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