Gluten is an amorphous ergastic protein found combined with starch in the endosperm of some cereals, notably wheat, rye, and barley. It constitutes about 80% of the proteins contained in wheat and is composed of the proteins gliadin and glutenin. Gluten is responsible for the elasticity of kneaded dough which allows it to be leavened, as well as the "chewiness" of baked products like bagels.
Gluten can be extracted from the flour of wheat and other grains by washing the starch out. To do this, a simple dough of flour and water is rinsed with plain water and kneaded until the rinsing water remains clear and free from starch and bran. For chemical, non-food purposes, a saline solution provides better results. The remaining lump of gluten should have a stringy, sticky texture reminiscent of chewing gum.
Cooked gluten becomes firm to the bite and soaks up a certain amount of the surrounding broth and its taste. It is therefore commonly used in vegetarian cuisine, notably Chinese Buddhist, and vegan cuisine where one variety is called seitan. Some consider it a convincing imitation meat (particularly duck) when the broth is flavored accordingly.
In the process of baking, gluten is responsible for keeping the fermentation gases in the dough, allowing it to rise. After baking, the coagulated gluten ensures that the final product keeps its shape.
Maladies and illnesses caused by gluten
People suffering from celiac disease have an intolerance to gluten and must go on a gluten-free diet. In their case, the gluten damages the mucosa of the small intestine, and as a result normal digestion becomes impossible. After avoiding gluten completely, the intestine will return to functioning normally.
People with autism and autistic spectrum disorders, like Asperger's syndrome, may be sensitive to gluten and casein (a protein in milk); both seem to have an opiate-like effect on these people. The opioid effect of gluten is caused by gluten exorphines and gliadorphin. These are peptides formed in the digestion of gluten. See more at gluten-free, casein-free diet. Another condition which may cause one to follow a gluten-free diet is dermatitis herpetiformis.
Gluten is found in some cereals (e.g., wheat, rye, barley) and their end products. No gluten is contained in rice (even glutinous rice), wild rice, maize (corn), millets, buckwheat, quinoa, or amaranth. Oats and teff do not contain gluten, but are sometimes grown directly adjacent to, and/or milled on the same equipment as, other grains that do contain gluten, and so are commonly contaminated. Non-cereals such as soybeans and sunflower seeds contain no gluten.
Many people who are unable to digest gluten and thus avoid wheat are able to digest kamut or spelt.