Thermal inactivation kinetics of pectinesterase extracted from oranges

A study was carried out on the kinetics of thermal inactivation of pectines terase (PE), extracted from the pulp of Valencia and Navel oranges. Moreove r, the influence of intrinsic factors on the kinetics of Navel orange PE wa s investigated. In a citric acid buffer, at a pH of 3.7 and 4.2, the enzyme was more thermostable as compared to water. However, at pH 3.2 an increase d inactivation and an increased temperature sensitivity of the rate constan t was observed. Ca2+-ions also enhanced the inactivation, whereas the tempe rature sensitivity of the rate constant decreased. In presence of sucrose, a diminished inactivation of PE was observed, and addition of sucrose only slightly influenced the activation energy.