Effect of high pressure treatments on peroxidase and polyphenoloxidase activities

The effects of hydrostatic pressure of 1-9 kbar on peroxidase (POD) and polyphenoloxidase (PPO) activity were studied. Trials were carried out on crude enzymatic extracts obtained from carrots and apples as the sources of POD and PPO, respectively, with different pH values (from 4.5 to 7.0). In both cases pressurization caused a remarkable enzyme activation after 1-min treatments carried out at 3-5 kbar, while a complete enzyme inactivation was observed at 9 kbar. The pH values of the crude enzymatic extracts seemed to affect the degree of activation and/or inactivation due to different pressure levels. A slight recovery in enzyme activity was measured for POD samples during the first 24 h of storage after the treatments