Effect of high pressure treatment on peroxidase (POD) activity in pear juice

A study was carried out about the effect of high hydrostatic pressure treatment (0.1～500 MPa) under temperature 20～60℃ and dwell time 2～34 min on peroxidase (POD) activity of Chinese Dangshan pear juice with different pH (3.0～7.0). Results showed that the peroxidase was activated when the high pressure treatment of the pear juice was carried out under the temperature 50℃, the dwell time 10 min, the pH 5 and the pressure less than 300 MPa; while its activity elevated. On the contrary, when the pressure more than 300 MPa, the peroxidase activity increased with the increase of pressure. High pressure treatment under temperature of less than 40℃ did not remarkably affect the peroxidase activity; contrarily, under temperature of more than 40℃ it was affected remarkbly. The peroxidase residual activity did not remarkably be decreased when the dwell time was longer than 10 min in the high pressure treatment. The peroxidase is the most pressure-resistant under pH 6. High pressure treatment at 500 MPa under 50℃, pH 3 for 10 min has a good ability to inactivate peroxides in the experimental conditions, and it is the optimal high pressure procedure to Chinese Dongshan pear juice.