Impact of ohmic heating on mass transfer in electroporated plant tissue-insights from numerical modelling

Abstract

Electroporation, electropermeabilization or pulsed electric field treatment is the application of electric pulses of sufficient amplitude to target tissue, which entails not only permeabilization of cell membranes, but also heat generation and dissipation, i.e. ohmic heating. Noticeable rise in temperature has been observed in a number of electroporation applications. The temperature rise is a potential source of alteration of thermodynamic properties of tissue wherein mass transport is occurring. In example, transport parameters such as liquid viscosity and solute diffusivity are temperature-dependent, as they relate to thermodynamic processes. There is a need to evaluate whether the rate of mass transport is altered significantly by the elevated temperature in plant tissue electroporation. The goal is to advance the basic knowledge of the phenomenon, as well as to optimize further treatment protocols for industrial purposes. This work presents a theoretical study of thermal relations in tissue immediately following electroporation and begins with a hypothetical spatio-temporal distribution of temperature in a sample of plant tissue as calculated during the course of a simulated electroporation experiment. This step is followed by a mass transfer analysis, where two mathematical models of mass transport in electroporated tissue are used to study the impact of transiently elevated temperature to i) kinetics of diffusion of a test solute, and ii) kinetics of liquid redistribution in tissue and its flow to sample exterior caused by an externally applied pressure. The main result of the study is a detailed theoretical analysis on the potential influence of heat generated due to the application of electroporation on kinetics of mass transport in tissue. Preliminary theoretical findings of this mass transport study coupled to the heat transfer model indicate that, provided the initial temperature increase in tissue is within reasonable bounds and heat is rapidly conducted away from tissue (i.e. tissue is not thermally insulated), influence of the temperature rise to mass transport in treated tissue is negligible.