title: Thermal isoelectric precipitation of alpha-lactalbumin from a whey protein concentrate: Influence of protein-calcium complexation.
abstract: The selective precipitation of alpha-lactalbumin (alpha-LA) at a pH around its isoelectric point (4.2) under heat treatment is the basis for a fractionation process of whey proteins. As precipitation is a phenomenon dependent on the protein hydrophobicity, and as the release of the tightly bound calcium occurring at pH around 4 modifies the alpha-LA hydrophobicity, the specific role of calcium on isoelectric precipitation is investigated. A study of the extent of alpha-LA precipitation in a whey protein concentrate under various operating conditions of pH, temperature, protein concentration, and calcium content is presented. We propose a mechanism for this phenomenon as a combination of a complexation equilibrium and of an irreversible precipitation, to account for the influence of temperature, alpha-LA concentration total ionic content, and calcium concentration, and also to estimate the complexation equilibrium constant. (c) 1995 John Wiley & Sons, Inc.
authors.affiliation: Centre National de la Recherche Scientifique, Laboratoire de Génie Chimique et Electrochimie, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Bramaud
authors.forename: P
authors.initials: P
authors.lastname: Aimar
authors.forename: G
authors.initials: G
authors.lastname: Daufin