alpha1casein

Alpha-1-casein, also known as alpha-S1-casein, is a phosphoprotein and one of the major protein components of milk in many mammals. It belongs to the casein family and is a key constituent of the casein micelle, a calcium-phosphate–rich complex that stabilizes milk and supplies calcium to the offspring. As a secreted milk protein, alpha-1-casein participates in micelle formation together with other caseins and minerals, influencing milk stability, viscosity, and coagulation during processing.

Chemically, alpha-1-casein is a relatively small, acidic protein that is highly phosphorylated at serine residues. The phosphate groups bind calcium ions, which helps drive the assembly and stability of the casein micelle. Its amino acid composition and phosphorylation pattern contribute to the protein’s functional properties in milk, including its interaction with other caseins and with rennet during cheese production.

Genetically, the CSN1S1 gene encodes alpha-1-casein in many species. The gene exhibits polymorphism, and different alleles can result in varying expression levels of alpha-1-casein among breeds or individuals. These variations can alter the overall milk protein profile, affect cheesemaking properties such as coagulation and yield, and influence allergenicity in sensitive individuals.

Ecologically and economically, alpha-1-casein is present in the milk of many mammals and varies in abundance across species and breeds. It remains a focus in dairy science and animal breeding due to its role in nutritional quality, processing characteristics, and the physical behavior of milk during storage and cheese production.