Combined effects of temperature and high-pressure treatments on physicochemical characteristics of skim milk

The combined effects of temperature (4, 20 and 40 °C) and high-pressure treatments (250, 450 and 600 MPa for 30 min) on the physicochemical characteristics of skim milk were studied. At 4, 20 and 40 °C, the effects of high-pressure treatments were similar (except for the treatment at 250 MPa), leading to an increase in protein hydrophobicity, a decrease in lightness, a decrease in average diameter of particles and slight solubilization of calcium and phosphorus from the colloidal to the aqueous phase of the milk. At the same time, denaturation of β-lactoglobulin probably occurred. At 40 °C, and especially at 250 MPa, the effects were very different because protein hydrophobicity remained unchanged and the average diameter of particles increased with the presence of two distinct populations of casein micelles. These results are discussed in relation to the effect of high-pressure treatments on protein structure.