Gluten is an ergastic amorphous mixture of proteins 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. It is the glutenins (specifically, high molecular weight glutenins) that are especially critical to gluten quality.

Extraction
It is possible to extract Gluten from the flour of wheat and other grains by washing out the starch. 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.

Usage
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 Buddhist cuisine and vegan cuisine, where one variety is called seitan, from Japanese. Some consider it a convincing imitation meat (particularly duck) when the broth is flavored accordingly.

In the process of baking with yeast, 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 (although starch is also essential for structural integrity). Recently, gluten has also been implicated as being at least partially responsible for bread staling.

Occurrence
Gluten is found in some cereals (e.g., wheat, rye, barley) and their end products. Wheat grown in countries with extreme weather conditions, such as Canada, tends to have a higher gluten content than wheat grown in countries where the winter is milder. Wheat flour with a high gluten content is called "strong" or "hard" flour, and is used for breads, whereas flour with a lower gluten content is called "soft" flour, and is used for cakes. No gluten is contained in rice (even glutinous rice), wild rice, maize (corn), millets, buckwheat, quinoa, sorghum, 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. Oats lack many of the prolamines found in wheat; however, oats do contain avenin. Avenin is a prolamine which is toxic to the intestinal submucosa and can trigger a reaction in some celiacs. Non-cereals, including legumes such as soybeans and seeds such as sunflower seeds, contain no gluten.

Other varieties of wheat such as kamut and spelt have slightly different forms of gluten. The gluten in spelt is more fragile than that found in wheat, and the bread dough can therefore collapse if overmixed.[citation needed] Many people who are unable to digest gluten for non-celiac reasons are often able to digest these varieties. People suffering from coeliac disease are advised to avoid all forms of gluten.

Health
In Celiac (or Coeliac) disease, an immune-mediated reaction to gliadin leads to damage to the lining of the small intestine. It is treated with a lifelong gluten-free diet.