Impact of insulator shape, flow rate and electrical parameters on inactivation of E. coli using a continuous co-linear PEF system

Pulsed electric field (PEF) application for the treatment of liquid media was investigated with focus on the improvement of the microbial inactivation.The paper aims to illustrate the various interdependencies of different treatment parameters such as electric field strength distribution, flow velocity profile, pulse energy, pulse frequency and electrical conductivity.Escherichia coli was used as an indicator microorganism to exemplify the impact of the previously mentioned parameters on the microbial inactivation results.The experimental set up was assisted by the numerical simulations of the electric field strength and flow velocity distribution. Two different configurations of insulator have been investigated related to the electric field strength and velocity distribution and their impact in the inactivation of E. coli.The convex insulator geometry was found to increase the average electric field strength from 37.6 to 38.5 kV/cm, but resulted in lower field homogeneity. Its use was therefore found to be favourable for the treatment media with lower conductivity. In that case, the application of a higher pulse number at maintained total specific energy input compensated field inhomogeneity effects by a longer treatment time.Industrial relevance: PEF as a non-thermal pasteurization technology requires an accurately defined treatment intensity in terms of electric field strength and treatment time. The microbial inactivation depends on the various interdependencies of different treatment parameters such as electric field strength distribution, flow velocity profile, pulse energy, pulse frequency and electrical conductivity. The presented investigation contributes to the understanding of these parameters for further successful industrial implementation of the PEF technology, such as, the proper selection of insulator shape, electric field strength and estimation of treatment time.

Research Highlights
► We studied the impact of the insulator shape on continuous PEF treatments.
► We modelled the impact of two treatment chambers of co-linear kind on E. coli.
► Insulator shape alters electric field strength, velocity and temperature.
► Increasing flow rate improved microbial inactivation.
► Insulator shape should be selected according to liquid media electrical conductivity.