Correlated percolation patterns in PEF damaged cellular material

We present results of numerical and experimental investigation of the electric breakage of a cellular material in pulsed electric fields (PEF). The numerical model simulates the conductive properties of a cellular material by a two-dimensional array of biological cells. The application of an external in the form of the idealised square pulse sequence with a pulse duration t i , and a pulse repetition time ∆t is assumed. The simulation model includes the known mechanisms of temporal and spatial evolution of the conductive properties of different microstructural elements in a tissue. The kinetics of breakage at different values of electric field strength E, t i and ∆t was studied in experimental investigation. A 5 mm x 55 mm cylindrical slab of apple is taken as a sample. The results of the experimental and numerical studies were compared. We propose the hypothesis for the nature of tissue properties evolution after PEF treatment and consider this phenomena as a correlated percolation, which is governed by two key processes: resealing of cells and moisture transfer processes inside the cellular structure. The breakage kinetics was shown to be very sensitive to the repetition times ∆t of the PEF treatment. We observed correlated percolation patterns in a case when ∆t exceeds the characteristic time of the processes of moisture transfer and random perco-lation patterns in other cases. The long-term mode of the pulse repetition times in PEF treatment allows us to visualize experimentally the macroscopic percolation channels in the sample. We observe considerable differences between the damage kinetics at long and short repetition times both for experimental and simulation data.