Electrophysiological Model of Intact and Processed Plant Tissues: Cell Disintegration Criteria

TLDR

Biological membrane electrical properties determine how cell system conductivity varies with alternating current frequency. The study presents frequency‑conductivity relationships of food cell systems derived from impedance measurements that capture Maxwell‑Wagner polarization at intact membrane interfaces. An equivalent circuit model of a single plant cell was used to measure conductivity spectra (3 kHz–50 MHz) of intact tissues and to predict conductivity changes for mixtures of intact and ruptured cells, enabling calculation of a cell disintegration index from low‑ and high‑frequency conductivities at 3 kHz and 12.5 MHz to assess disruption from various treatments.

Abstract

Frequency versus conductivity relationships of food cell system, based on impedance measurements as characterized by polarization effects of the Maxwell−Wagner type at intact membrane interfaces, are presented. The electrical properties of a biological membrane (represented as a resistor and capacitor) are responsible for the dependence of the total conductivity of the cell system on the alternating current frequency. Based on an equivalent circuit model of a single plant cell, the electrical conductivity spectrum of the cell system in intact plant tissue (potato, carrot, banana, and apple) was determined in a frequency range between 3 kHz and 50 MHz. The electrical properties of a cell system with different ratios of intact/ruptured cells could also be predicted on the basis of a description of a cell system consisting of elementary layers with regularly distributed intact and ruptured cells as well as of extracellular compartments. This simple determination of the degree of cell permeabilization (cell disintegration index, po) is based upon electric conductivity changes in the cell sample. For accurate calculations of po, the sample conductivities before and after treatment, obtained at low- (fl) and high-frequency (fh) ranges of the so-called β-dispersion, were used. In this study with plant cell systems, characteristic conductivities used were measured at frequencies fl = 3 kHz and fh = 12.5 MHz. The disintegration index was used to analyze the degree of cell disruption after different treatments (such as mechanical disruption, heating, freeze−thaw cycles, application of electric field pulses, and enzymatic treatment) of the plant tissues.