Combined pressure-temperature inactivation of alkaline phosphatase in bovine milk: A kinetic study

A detailed kinetic study on pressure-temperature inactivation of alkaline p hosphatase has been performed in the pressure range 0.1 to 725 MPa at tempe ratures between 25 and 63 degrees C. Inactivation could be accurately descr ibed by a first order kinetic model, allowing D-values to be calculated. Ac cording to the thermal death time terminology, z(T)- and z(P)-values were c alculated, expressing temperature and pressure dependence respectively. How ever, at high temperature, pressure dependence could not be calculated unam biguously. D-values firstly increased with increasing pressure up to 300 MP a and then decreased with further pressure increase, showing thermal inacti vation to be counteracted by low pressure. Finally, a global model describi ng the D-value as a function of pressure and temperature has been formulate d.