Pulsed electric field treatment of Saccharomyces cerevisiae suspensions: A mechanistic approach coupling energy transfer, mass transfer and hydrodynamics

Pulsed electric field (PEF) treatment is a promising sterilization technique because of its nonthermal characteristics. It is well known that PEF applied at field values about 30 × 105 V m−1 promotes cell disruption, internal component leakage, and subsequent death. Classically, lethality is only related to electric and biological parameters. However, it is conceivable that hydrodynamic or process parameters are also involved. The goal of this work was therefore to understand the synergetic effects between electric energy transfer and hydrodynamics, based on trials carried out with a model biomass composed of Saccharomyces cerevisiae yeast treated in an experimental set-up.This work demonstrates that survival rates can be drastically decreased at constant electric energy input, by strong mixing between each pulse. Taking into account the cell permeabilization, leakage phenomena were considered through internal component diffusion and convection from the biologic cell to the surrounding medium. A new approach was therefore proposed in which the survival rate was associated with a modified Sherwood number. For the first time with PEF treatment, this approach integrated all kinds of parameters: biological (mainly through the cell radius), electrical (through the electric field and electrical resistance), and hydraulic (through the Reynolds number and number of recyclings). Finally, this study contributes to optimizing the specific energy consumption, making the PEF sterilization process more efficient.