Abstract The thermal inactivation kinetics of purified Aspergillus aculeatus pectin methylesterase (PME) was investigated. In the temperature range 46–56 °C A. aculeatus PME inactivates following a first-order reaction. Addition of CaCl 2 (50 mM or 1.0 M) has no noticeable influence on the inactivation parameters. A. aculeatus PME is very pressure stable, at 25 °C no loss of activity was noticed after pressurization at 700 MPa for 1 h. Pressure and temperature exhibit an antagonistic effect on the enzyme stability. Furthermore A. aculeatus PME was unsusceptible for inhibition by PME inhibitor purified from kiwi.