Casein is the principal protein found in milk. It is responsible for the white, opaque appearance of milk. It is combined with calcium and phosphorus in clusters termed micelles. Until the 1960s, casein was primarily used in technical, nonfood applications, such as adhesives for wood, paper coating, leather finishing, synthetic fibers, and plastics. But in the last 30–35 years, casein has been principally employed in food applications as an ingredient for enhancing the food’s physical properties, including whipping and foaming, water binding and thickening, emulsification and texture. Casein also improves a food’s nutritive value.