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 degrees C), and denaturation of beta-lactoglobulin A and B and alpha-lactalbumin were analyzed. Kinetic parameters were determined by means of a one step non-linear regression. Denaturation of beta-lactoglobulin and alpha-lactalbumin were found to follow second and 2.5 order kinetics, respectively. Heat- and pressure-induced denaturation of both beta-lactoglobulin fractions did not differ significantly and alpha-lactalbumin was more resistant to denaturation than beta-lactoglobulin. The activation volume. Delta V-not equal, for denaturation of beta-lactoglobulin decreased from zero to -80 m L mol(-1) with increasing temperature. Activation energy, E-A, of denaturation of beta-lactoglobulin calculated at various pressures exceeded 200 U mol(-1) at 100 and 200 MPa and decreased at higher pressures, to about 100 U mol(-1), indicating that high pressure promotes unfolding of the molecules. (C) 2004 Elsevier Ltd. All rights reserved.