Kinetics of combined thermal and pressure-induced whey protein denaturation in bovine skim milk

A detailed kinetic study of combined pressure and temperature treatment of milk was carried out in order to estimate kinetic parameters for the denaturation of whey proteins. Skim milk was treated under isobaric conditions (200-800 MPa) in combination with isothermal conditions (1-70 °C), and denaturation of β-lactoglobulin A and B and α-lactalbumin were analyzed. Kinetic parameters were determined by means of a one step non-linear regression. Denaturation of β-lactoglobulin and α-lactalbumin were found to follow second and 2.5 order kinetics, respectively. Heat- and pressure-induced denaturation of both β-lactoglobulin fractions did not differ significantly and α-lactalbumin was more resistant to denaturation than β-lactoglobulin. The activation volume, ΔV#, for denaturation of β-lactoglobulin decreased from zero to −80 mL mol−1 with increasing temperature. Activation energy, EA, of denaturation of β-lactoglobulin calculated at various pressures exceeded 200 kJ mol−1 at 100 and 200 MPa and decreased at higher pressures, to about 100 kJ mol−1, indicating that high pressure promotes unfolding of the molecules.