Pulsed Electric Fields

Pulsed electric field treatment of food material involves the application of short pulses (microseconds) of high voltage (kilovolt). When exposed to such electric field pulses cell membranes develop pores which may be permanent or temporary, depending on the intensity and treatment conditions. The possible application of this non-thermal technology in a wide range of the food industry is based on this effect on biological cells which is called electroporation (see Fig. 1). The pore formation increases membrane permeability which results in the loss of cell content or intrusion of surrounding media.

Low treatment intensity allows a reversible disturbance of the phospholipids bilayer, which is routinely used as tool in molecular biology to introduce polar molecules like DNA into a host cell through the cell membrane.  The quick voltage shock disrupts areas of the membrane temporarily but then the membrane may reseal quickly and leave the cell intact. Recent investigations showed the potential of this low intensity treatment to induce stress reactions in plant cells resulting in the promotion of a defence mechanism by increased production of secondary metabolites.

An irreversible perforation of the cell membrane reduces its barrier effect permanently and causes cell death. Applied to fruit and vegetable cells mass transfer processes like pressing, extraction or drying are more effective, in the case of meat brining and pickling mass transport and microdiffusion could be enhanced. The loss of cell vitality caused by electroporation is furthermore a capable tool for the non-thermal inactivation of microorganisms used for a mild preservation of liquid food.

The concept of electroporation and its application in the food industry is investigated for more than 40 years. Major research work was necessary in order to understand basic mechanisms and develop reliable processing concepts. Major improvements have been made regarding the availability of suitable equipment in the last years and first industrial applications have been realised in the fruit juice industry for cell disintegration and in liquid food processing for non-thermal pasteurisation.

 


This text was prepared by Henry Jaeger, of the Berlin Institute of Technology (Technische Universität Berlin), Department of Food Biotechnology and Food Process Engineering, Berlin, Germany.


 

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