Thermal inactivation of exogenous pectin methylesterase in apple and cloudberry juices

The stability and inactivation kinetics of exogenous Aspergillus niger pectin methylesterase in fruit juices was studied in the temperature interval of 52–66 °C. The temperature treatment was applied to two kinds of non-pasteurized apple juices, two cloudberry juices and 0.1 M acetate buffer for the assessment of the influence of juice components on the enzyme stability. The enzyme was very thermally labile in the studied temperature range with the z-value around 7 °C. The composition of juices caused a considerable difference in the enzyme susceptibility to thermal inactivation. The enzyme inactivation however followed first-order kinetics with approximately the same value of the activation energy of 300 kJ/mol for each material.