Electric measurement of the electroporation efficiency of mash from wine grapes

The degree of cell opening after electroporation can be derived from an electric impedance measurement in a frequency range between 500 Hz and 10 MHz. For a simple detection in a continuously flowing medium a measurement at a discrete frequency evaluating the phase shift between a measurement voltage across an electrode system and a current flowing through the sample volume has been investigated. The paper describes impedance measurements of the mash of wine grapes. For different grape varieties the frequency dependency of the phase shift has been measured. The data showed that the frequency of maximum phase shift differs with the grape variety. For the mash of wine grapes the measurement results based on the measurement of the complex impedance have been compared to the degree of extraction of color from the peel tissue of red wine grapes as a conventional method to determine the degree of denaturation. The measurements showed a correspondence between the color intensity of the must and the electric measurements.