High pressure and temperature effects on enzyme inactivation in strawberry and orange products

High hydrostatic pressure treatment (50-400 MPa) combined with heat treatment (20-60 degrees C) effects on peroxidase (POD), polyphenoloxidase (PPO) and pectin methylesterase (PME) activities of fruit-derived product were studied. Assays were carried out on fresh orange juice and strawberry puree. Pressurization/depressurization treatments caused a significant loss of strawberry PPO (60%) up to 250 MPa and POD activity (25%) up to 230 MPa, while some activation was observed for treatments carried out in 250-400 MPa range for both enzymes. Optimal inactivation of POD was using 230 Mpa and 43 degrees C in strawberry puree. Combinations of high pressure and temperature effectively reduced POD activity in orange juice (50%) to 35 degrees C. The effects of high pressure and temperature on PME activity in orange juice were very similar to those for POD.