Inactivation and conformational change of pectinesterase induced by pulsed electric fields

To research the application of non-thermal processing technology on the processing of fruit and vegetable juices, the effects of pulsed electric field (PEF) on the activity and structure of pectinesterase (PE) in buffer solution were studied. The results showed relative activity of PE decreased with the increase in applied electric field intensity (5～25 kV/cm) and pulse numbers (207～1449). 65.3% reduction of PE relative activity was achieved immediately after PEF treatments at 25 kV/cm 207 pulses. The relative activity exhibited no significant difference after 48 h storage at 4℃. Relative activity change of PE had good correlation with electric field intensity and pulse numbers, and the values of R² were 0.988 and 0.953, respectively. The PE conformation changed after PEF treatment as suggested by fluorescence spectroscopy analysis. The intrinsic fluorescence intensity increased after PEF treatment (621 pulse numbers) and heat reatment(100 ℃ for 5 min), reaching 157.4%, 507.9%, 368.7% and 584.2% at 5 kV/cm, 15 kV/cm, 25 kV/cm and 100 ℃ for 5 min, respectively. Therefore, PEF effectively decreased the activation of PE and changed the structure of PE.