Sensing of Yeast Inactivation by Electroporation

Abstract

Irreversible electroporation is a treatment to control microorganisms in food without harming food palatable aspects. The treatment by electroporation is dependent on the electric field amplitude, pulse durations and pulse repetitions. This study was carried out as a further investigation on the effects of irreversible electroporation pulse amplitude on S. cerevisiae and methods to verify the occurrence of irreversible electroporation, such as cell viability hemocytometer, macroscopic impedance measurements, scanning electron microscopy and numerical simulations. Active yeasts in wine represent a small portion of the volume (<; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cell/mL), which challenges macroscopic impedance analysis. Irreversible electroporation proved to reach active yeast limits established by standards within 500 kV/m. We detected a 15% increase in the in pulse current measurements for a 100-fold yeast viability decrease to 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cells/ml. Scanning electron microscopic images show details of yeast surface damage which may be PEF-triggered. Electric fields above 1 MV/m on the cell wall and release of intracellular substance caused by membrane permeability increase may directly contribute to yeast inactivation. Electroporation combined with instantaneous current-voltage measurements may be an adequate procedure for reducing yeast numbers in the industry.