Impact of a Pulsed Electric Field on Damage of Plant Tissues: Effects of Cell Size and Tissue Electrical Conductivity

Efficiency of pulsed electric field (PEF) induced permeabilization at 293 K in selected fruit and vegetable plant tissues (apple, potato, carrot, courgette, orange, and banana) at electric field strength (E) of 400 V.cm(-1), 1000 V.cm(-1) and pulse duration (t(p)) of 1000 mu s was studied experimentally. The mean cell radius (< r >) was within 30 to 60 mu m, and the ratio of electrical conductivities of the intact and damaged tissues (sigma(i)/sigma(d)) was within 0.07 to 0.79 for the studied tissues. Electroporation theory predicts higher damage for tissue with larger cells; however, the direct correlation between PEF damage efficiency and size of cell was not always observed. To explain this anomaly, a theoretical Monte Carlo model was developed and checked for parameters typical for potato tissue. The model showed a strong dependence of PEF damage efficiency and power consumption (W) on sigma(i)/sigma(d) ratio. The optimum value of electric field strength (E-opt) was an increasing function of si/sd, and plant tissues with high si/sd ratio (sigma(i)/sigma(d) approximate to 1) required application of a rather strong field (for example, E-opt approximate to 3000 V.cm(-1) for sigma(i)/sigma(d) approximate to 0.8). However, the PEF treatment at a lower field (E approximate to 400 V.cm(-1)) allowed regulation of the selectivity of damage of cells in dependence of their size. A good qualitative correspondence between experimental data and simulation results were observed.