Single strength orange juice was treated with supercritical carbon dioxide (CO2) and the effect of process time, temperature and pressure on pectinesterase (PE) activity was determined. PE could be inactivated with supercritical CO2 below temperatures necessary for thermal inactivation. Higher pressure, temperature and longer treatment time resulted in more inactivation. Inactivation kinetics showed activation energy was significantly reduced at SC C02 treatment at 31 MPa (97.4 KJ/mole), compared to identical treatments at atmospheric pressure (166.6 KJ/mole). D values ranged from 2673 min at atmospheric pressure and 40°C to 10 min at 31 MPa and 60°C. z value at atmospheric pressure was 8.8C°, and at 31 MPa 5.2C°.