As expected, noticeable depolymerization of highly esterified pectin (DE, 80%) catalyzed by tomato polygalacturonase was observed when active tomato pectinmethylesterase was present, which was not the case in absence of tomato pectinmethylesterase. Besides, an increase in polygalacturonase activity was observed up to an optimal pressure level (100-20OMPa) depending on the temperature under study. Only at higher pressures, the rate of enzymatic pectin depolymerization diminished. In presence of active tomato polygalacturonase a higher tomato pectinmethylesterase activity was observed than in absence of tomato polygalacturonase at atmospheric pressure. The pectinmethylesterase catalyzed pectin deesterification accelerates by increasing pressure up to 200 MPa in presence of tomato polygalacturonase. Higher pressures diminished the tomato pectinmethylesterase activity becoming even lower as compared to atmospheric pressure, which is in contrast with the pectinmethylesterase activity studies performed in absence of tomato polygalacturonase. In general, tomato polygalacturonase activity was influenced indirectly by the presence of active tomato pectinmethylesterase and vice versa during thermal and high-pressure treatment. The combination of 40 degrees C and 400 MPa represents an optimal condition to preserve or improve theological properties of tomato based products, because at this condition tomato polygalacturonase activity is reduced while pectinmethylesterase activity is maintained. (c) 2006 Elsevier Inc. All rights reserved.