Temperature–time relationships for thermal inactivation of pectinesterases in orange juice

The first-order kinetic model of a two-component system was applied to calculate the necessary parameters using the commercial Mathcad program package during the experimental thermal pasteurisation of Valencia orange juice. Thermostable and thermolabile pectinesterases, accounting for 6.6 and 93.4% of the total enzyme population in the juice respectively, showed a 5.63 °C Z(s) value and a 9.54 °C Z(l) value respectively from the thermal destruction curves at temperatures ranging from 75 to 90 °C. The calculated Z(s) values were consistent with the literature values for Valencia orange juice. The calculated and experimental non-linear thermal pasteurisation curves for orange juice were also in good agreement at temperatures between 75 and 90 °C.