betacasein

Betacasein, also known as beta-casein, is one of the major proteins in milk. It accounts for roughly one-third of the casein fraction in bovine milk and is produced by mammary gland cells in many mammals. The betacasein protein is encoded by the CSN2 gene and is a principal component of casein micelles, which also include alpha-caseins and kappa-casein and are stabilized by calcium phosphate. These micelles are central to dairy processing and influence the texture of dairy products such as cheese.

Genetic variation exists in betacasein. The best-known variants are A1 and A2, which differ by a single amino acid at residue 67 of the mature protein (A1 has histidine; A2 has proline). During digestion, A1 betacasein can release beta-casomorphin-7, an opioid-like peptide, more readily than the A2 form; health claims related to BCM-7 are controversial and not conclusively supported by robust evidence.

Betacasein can be an allergen for some people with cow’s milk allergy, though lactose intolerance is a separate issue. In dairy processing, betacasein remains a major component of micelles and contributes to protein structure; proteolysis during aging and processing yields various bioactive peptides that have been studied for potential effects.