Pressurisation of raw skim milk and of a dispersion of phosphocaseinate at 9 °C or 20 °C: effects on the distribution of minerals and proteins between colloidal and soluble phases

Abstract

The effects of high pressure treatments (100–300 MPa; 15 min; 9 °C or 20 °C) on the distribution of minerals and proteins of raw skim milk (RSM) and of a dispersion of industrial phosphocaseinate (PC) were studied after separation of the micellar and soluble phases by ultracentrifugation (UCF). Whatever the temperature of high pressure treatments, the pressure-induced dissociation of the casein micelles was accompanied by calcium (Ca), phosphorus (P) and casein release from the micelles. The released Ca and P were or became bound to soluble proteins since progressive increases in Ca and P concentrations were observed in the UCF supernatants of RSM and of the PC dispersion but not in the ultrafiltrates from these UCF supernatants (free of soluble proteins). Simultaneously, α_S1-, α_S2-, β- and κ-caseins were progressively released from the micelles, as seen by electrophoretic analysis. The pressure-induced solubilisation of α_S1- and α_S2-caseins, essentially located in the core of the micelles, suggests that high pressure destabilised micelles including their internal structure.