Paper title

“Pulsed Electric Field (PEF) for microbial inactivation”

Authors: Professor Shesha H. Jayaram
Affiliation
:
Department of Electrical & Computer Engineering, University of Waterloo, Canada

Abstract - Microbial inactivation in liquid foods by PEF involves the application of pulses of high voltage to liquid food, so as to induce a substantially high electric field across the microbial cell membrane. We have been able to make significant contributions to the understanding of the kinetics of microbial inactivation and the theory of membrane breakdown. The paper, "Kinetics of sterilization of Lactobacillus brevis by the application of high voltage pulses”, Biotechnology & Bioengineering, Vol. 40, pp. 1412-1420, 1992 on kinetics of sterilization has been referenced more than 80 times. The synergetic effect of thermal and electrical fields has been demonstrated for the first time. In addition, two major multinational processors of pure fruit juices, drinks and dairy products have been working together to implement the PEF technology. With support from these two companies, the use of a non-thermal pasteurization and sterilization of liquid foods using PEF will continue to contribute to the processing of liquid foods.

Electrostatics in Process Technology:

A wide range of industries use high voltages and often encounter problems needing solutions that are very diverse. These include advanced electrostatic precipitators (ESP), Flue gas cleaning systems, and water purifying systems. A novel electron beam technology was developed for water treatment, as were special sources to generate superimposed pulses on DC voltage for ESP energization for ultra fine particle collection. High voltage applications in electrospinning to fabricate nanomaterials are the new directions taken in collaboration with the Food Science Research group at the University of Guelph.

Treatment chambers for PEF Pasteurization:

The limitations to the industrial application of the PEF process are the generation of high electric fields and the design of treatment chambers that impart uniform exposure of foods to high electric fields, without increasing the temperature of the liquid food. Our work has provided solutions to these critical problems. We have developed a continuous PEF process system using the novel treatment chamber. The uniqueness of this chamber is that the electrode geometry has no edge effects; yet provides substantially high electric fields with smooth electrode surfaces. Providing laminar flow and uniform exposure of medium to sufficiently high electric fields has been accomplished.

Diagnostic methods to detect early degradation of insulation:

In the field of insulation, the focus is on understanding the pre-breakdown mechanisms in polymeric insulating materials. We have developed the partial discharge diagnostic method to detect the loss of hydrophobicity, inception of dry band arcing, and hence the degradation more effectively than other conventional methods that are being currently used in the industry. Also, we have used a novel approach based on harmonic analysis of leakage current to identify the dangerous levels of arcing activities on the surface of polymeric insulation, which allows one use the third harmonic component as an index to monitor the conditions on high voltage insulators.

Laser based technique to evaluate the composite materials:

The conventional ASTM D2303 is an inclined plane test method usually used for evaluating the tracking and erosion resistance of materials by subjecting the materials to a combination of contaminant and voltage. The combination of voltage and contaminant flow leads to continuous occurrence of dry band arcing over the surface of samples, thus simulating the conditions of degradation due to dry band arcing in the field, but in an accelerated way. The test involves a series of steps over a prolonged period of about four hours. We have developed a new methodology for evaluating insulating materials using an Infra Red laser source. Our laser technique offers significant advantages and it is fast, simple, and reproducible.