Betalactoglobulin

Beta-lactoglobulin is the major whey protein of cow's milk and other ruminant milks. It is a small globular protein of about 18-19 kDa and consists of about 162 amino acids. It belongs to the lipocalin superfamily, characterized by a conserved beta-barrel structure with a hydrophobic pocket that binds small hydrophobic ligands such as fatty acids, retinoids, and aroma compounds. The protein contains disulfide bonds that help stabilize its fold and can exist as a monomer or form higher-order aggregates depending on pH and temperature. In milk, beta-lactoglobulin is produced in the mammary gland and constitutes a major fraction of whey protein; it is notably absent from human milk.

In terms of function, beta-lactoglobulin acts as a carrier for hydrophobic ligands in milk and may play a role in the transport or sequestration of volatile or lipid-like compounds, affecting flavor and nutrition. It is also a well-known allergen; beta-lactoglobulin is a major cause of cow's milk allergy and is relatively resistant to heat and proteolysis compared with some other milk proteins, though processing can alter its allergenicity.

Industrially, beta-lactoglobulin is widely used as a dietary protein supplement and as a functional ingredient in dairy and food products. It is also a common model protein in structural biology due to its stability and well-characterized structure.