Gluten (from Latin gluten, "glue") is a group of proteins, called prolamins and glutelins, which occur with starch in the endosperm of various cereal grains. This protein complex comprises 75–85% of the total protein in bread wheat. It is found in related wheat species and hybrids, (such as spelt, khorasan, emmer, einkorn, and triticale), barley, rye, and oats, as well as products derived from these grains, such as breads and malts.
Glutens, especially Triticeae glutens, have unique viscoelastic and adhesive properties, which give dough its elasticity, helping it rise and keep its shape and often leaving the final product with a chewy texture. These properties and its relative low cost are the reasons why gluten is so widely demanded by the food industry and for non-food uses.
Prolamins in wheat are called gliadins; in barley, hordeins; in rye, secalins; and in oats, avenins. These protein classes are collectively referred to as gluten. Wheat glutelins are called glutenin. True gluten is limited to these four grains. (The storage proteins in maize and rice are sometimes called glutens, but they differ from true gluten.)
Gluten can trigger adverse inflammatory, immunological and autoimmune reactions in some people. Gluten can produce a broad spectrum of gluten-related disorders, including coeliac disease in 1–2% of the general population, non-coeliac gluten sensitivity in 6–10% of the general population, dermatitis herpetiformis, gluten ataxia and other neurological disorders. These disorders are treated by a gluten-free diet.