Gluten is usually defined as being a protein in wheat, barley and rye, but really, gluten is a mixture of two types of proteins: prolamins and glutelins. Gluten is found in all grains, but while the prolamins in rice and corn gluten are safe for celiac patients, the prolamins in wheat (called gliadin), barley (called hordein), and rye (called secalin) are not. In people with celiac disease, these protein molecules in wheat, barley and rye trigger an autoimmune response that results in damage to the small intestine, along with other related problems.
For people without celiac disease, gluten is an important source of nutritional protein, both in foods that contain gluten as a main ingredient, and in foods that contain gluten as an additive to increase the protein content.
Gluten has a variety of qualities that are important for baked goods and other foods. It helps make dough elastic, provides it with a chewy texture, helps it rise before it is baked and helps ensure that baked goods maintain their proper shape. Gluten also has an absorbent quality, which lets bread soak up gravy and donuts soak up coffee.
