Pulse Duration and Efficiency of Soft Cellular Tissue Disintegration by Pulsed Electric Fields

The effect of pulse duration on efficiency of disintegration of apple tissue by pulsed electric fields (PEF) was studied. The samples (26-mm diameter, 10-mm height) were treated by PEF at electric field strength E between 100 and 400 V/cm, pulse duration t(i) of 10, 100, 1,000 mu s, interpulse duration Delta t of 100 mu s and different number of pulses n. Both the degree and the time evolution of tissue damage were quantified by electrical conductivity disintegration index Z and characteristic damage time tau, respectively. The samples exposed to the same PEF treatment time nt(i) showed noticeably higher disintegration efficiency for larger pulse duration. The synergism of PEF and thermal treatment with temperature T (20-50 degrees C) was demonstrated. The Arrhenius dependence of t(T) for PEF treatment at E=100 V/cm gave the decreasing activation energy W as a function of ti, (Q approximate to 164 kJ/mol at t(i) = 10 mu s, Q approximate to 109 kJ/mol at t(i) = 100 mu s and Q approximate to 66 kJ/mol at t(i) = 1,000 mu s). Textural relaxation data supported the higher damage efficiency for longer pulse duration.