caseins

Caseins are a family of phosphoproteins that constitute the major protein fraction of milk from cows and many other mammals. They account for roughly 80% of milk protein and occur as a heterogeneous group of four principal polypeptides: alpha-s1-, alpha-s2-, beta-, and kappa-casein, along with minor gamma-caseins formed by post-translational modification. Caseins are amphiphilic and interact with calcium phosphate to form casein micelles, colloidal aggregates that calcium and phosphate stabilize. This micellar assembly serves as a reservoir for calcium and phosphate and underpins dairy processing, especially cheese making. When milk is acidified or treated with rennet, kappa-casein is cleaved, destabilizing micelles and causing coagulation to form curds.

Different processing routes yield various casein products. Acid casein is precipitated with acidic conditions and removed from the whey; rennet casein is produced by enzymatic precipitation. Industrially, caseins and caseinates (such as calcium or sodium caseinate) are used as functional ingredients in foods for texturizing, emulsification, and protein fortification. Casein hydrolysates are produced for nutritional supplements and specialized foods.

Nutrition-wise, caseins provide high-quality protein rich in essential amino acids, and they are relatively slow-digesting compared with whey proteins. Allergies to milk proteins frequently involve caseins and are a consideration in dietary restrictions; lactose intolerance is separate from casein sensitivity. In dairy technology, understanding casein properties is fundamental to milk processing, cheese manufacture, and the design of protein-based food ingredients.