Electrical Impedance Spectroscopy insight into plant tissues treated by Pulsed Electric Fields

Electroporation or pulsed electric field (PEF) treatment is known to cause an increase of cell membrane permeability and consequently an increase of the cell membrane conductivity. This is explained by the creation of aqueous pathways in the lipid domain of the cell membrane exposed to the external electric field. Since the cell membrane exhibits relatively high impedance, any permeabilization will result in a drop in impedance of the single cell and consequently of the tissue. Hence, the electroporation effect on biological matrices can be assessed by measurements of their electrical properties. The electrical impedance spectroscopy (EIS) has been suggested as a reliable method to estimate the extent of tissue damage due to high voltage treatment. This study reports on results of the bioimpedance measurements performed on different PEF-treated plant tissues (i.e. apples and potatoes). Furthermore, since bioimpedance depends on several physiological parameters, and changes in electrical properties can be masked by other processes, EIS was performed on a model system, i.e. an agarose phantom, lacking any cell structures and constituents. As expected, no changes of the measured electrical parameters were detected in the agarose samples. On the contrary, plant tissues showed a pronounced drop of the normalized impedance proportional to the electric field amplitude applied to the tissue.