High pressure thermal denaturation kinetics of whey proteins.

摘要

Effect of high pressure processing of milk on denaturation of whey proteins was investigated. Pressure and temp. dependent denaturation kinetics were determined separately. In a detailed kinetic study, whey protein isolate was treated under isobaric (200-800 MPa) and isothermal conditions (-2 to 70degC), and the resulting degree of denaturation of beta-lactoglobulin A and B and alpha-lactalbumin was analysed. Kinetic parameters of denaturation were estimated using a 1 step non-linear regression method which allowed a global fit of the whole data set. The isobaric isothermal denaturation of beta-lactoglobulin and alpha-lactalbumin was found to follow 3rd and 2nd order kinetics, respectively. Isothermal pressure denaturation of both beta-lactoglobulin fractions did not differ significantly and were characterized by a decrease in activation vol. with increasing temp. from -10 to approx. -30 ml/mol, which demonstrates that the denaturation rate is accelerated with increasing temp. The activation energy of approx. 70-100 kJ/mol obtained for beta-lactoglobulin A and B was not dependent to a great extent on the pressure; this indicates that at pressures >200 MPa, the denaturation rate is limited by the aggregation rate, while pressure forces the molecules to unfold.