A brown, water-insoluble, non-starchy portion of cereal grains, such as wheat, corn and rice. Gluten is composed of a mixture of 18 plant proteins. It is hygroscopic and will form an elastic dough when mixed with water. Gluten must be removed to make starch paste. Dilute aqueous mixtures of gluten have been used as adhesives. Prior to the 19th century, the term gluten was used to refer to an adhesive material.