Inactivation Effects of PEF on Horseradish Peroxidase (HRP) and Pectinesterase (PE)

The effect of pulsed electric fields (PEFs) applied on the enzymes horseradish peroxidase (HRP) and pectinesterase (PE), which widely exist in vegetable and fruit juices, was investigated using chambers with paralleled plane electrode and coaxial cylinder electrode, respectively. The experimental results show that the relative activity of HRP and PE decreased after PEF treatment. Inactivation effect of HRP and PE increased with the increase of the applied electric strength and the number pulses. HRP activity decreased 14.4% and 16.7% in the parallel-plane chamber and the coaxial cylinder chamber, respectively, at 207 pulses of 25 kV/cm, while a 17 (coaxial) and 16.46 (plane) reduction, respectively, was attained for PE under the same experimental condition. Inactivation effect of HRP and PE in the chamber with coaxial-cylinder-electrode configuration was better than the parallel-plane electrode. The circular-dichroism analysis showed that PEF treatment caused a loss of alpha-helix and change of the secondary-conformation structure of HRP enzyme. The fluorescence intensity of both enzymes also changed after PEF treatment, indicating that conformation changes occur in the local structure of the enzyme molecule