Comparison of the Effects of High Pressure and Thermal Treatments on the Casein Micelles in Goat's Milk

The influence of thermal and high-pressure treatments on caprine casein micellar structure and, in particular, on the micellar serum distribution of whey proteins, caseins, and calcium phosphate was studied by ultracentrifugation and transmission electron microscopy. Quantification of the major whey proteins and caseins was achieved using reverse-phase HPLC, and the extent of denaturation of the whey proteins was determined by gel permeation FPLC. Thermal treatment of goat's milk had little effect on the micellar serum distribution of caseins, but pressure treatment at 20 °C caused disruption of micelles into smaller particles and gave an increase in the amount of serum casein. Pressure treatments between 300 and 350 MPa at 45 °C caused the formation of very large micelles and gave an increase in the level of serum κ-casein. Higher pressure at 45 °C, however, caused disruption of the micelles, with the formation of smaller, less easily sedimented fragments. On pressure treatment, βLg was most easily denatured, and appreciable deinaturation of the immunoglobulins and α-lactalbumin only occurred at the higher pressures, particularly at 45 °C.