gluten, mixture of proteins present in the cereal grains. The long molecules of gluten, insoluble in water, are strong and flexible and form many cross linkages. This gives flour its characteristic chewiness and permits breads and cakes to rise during baking as the gases within expand and are trapped in the gluten superstructure. Various flours have different ratios of gluten to starch (called hardness) and are appropriate for different types of foodstuffs. Thus soft flour is used for cakes, harder flour for pastry, hard flour for bread, and the hardest, or durum, for pasta. The hereditary disease called nontropical sprue is characterized by an inability to digest gluten. In this disease the gluten acts as an antigen (see immunity) and forms immune complexes that cause damage to the mucus lining of the intestine.