Hypoallergenic and Physicochemical Properties of the A2 beta-Casein Fraction of Goat Milk

Abstract

Goat milk has a protein composition similar to that of breast milk and contains abundant nutrients, but its use in functional foods is rather limited in comparison to milk from other sources. The aim of this study was to prepare a goat A2 beta-casein fraction with improved digestibility and hypoallergenic properties. We investigated the optimal conditions for the separation of A2 beta-casein fraction from goat milk by pH adjustment to pH 4.4 and treating the casein suspension with calcium chloride (0.05 M for 1 h at 25 degrees C). Selective reduction of beta-lactoglobulin and alpha(s) was confirmed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis and reverse-phase high-performance liquid chromatography. The hypoallergenic property of A2 beta-casein fraction was examined by measuring the release of histamine and tumor necrosis factor alpha from BMC-1 human mast cells exposed to different proteins, including A2 beta-casein fraction. There was no significant difference in levels of both indicators between A2 beta-casein treatment and the control (no protein treatment). The A2 beta-casein fraction is abundant in essential amino acids, especially, branched-chain amino acids (leucine, valine, and isoleucine). The physicochemical properties of A2 beta-casein fraction, including protein solubility and viscosity, are similar to those of bovine whole casein which is widely used as a protein source in various foods. Therefore, the goat A2 beta-casein fraction may be useful as a food material with good digestibility and hypoallergenic properties for infants, the elderly, and people with metabolic disorders.