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Power source for inactivation of micro-organisms with partial high voltage discharge in a continuous process

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Author: Creyghton, Y. · Beurskens, R. · Fiala, A. · Haan, S.W.H. de
Type:article
Date:2002
Source:Gordon L., Conference Record of the Twenty-Fifth International Power Modulator Symposium and 2002 High-Voltage Workshop, 30 June 2002 through 3 July 2002, Hollywood, CA, Conference code: 60772, 657-661
Identifier: 236831
Keywords: Electric corona · Electric discharges · Electrodes · Food preservation · Microbiology · Microorganisms · Temperature · Bacillus subtilis · Lactobacillus plantarum · Liquid food pasteurization · Microbial inactivation · Partial high voltage discharge · Thermal arcing phase · Electric field effects

Abstract

An electrical discharge technology is investigated as non-thermal method for inactivation of microorganisms. Potential applications include treatment of drinking water (e.g. legionella) and liquid food pasteurization (e.g. fruit juices). A strong interest exists in mild food conservation processes without the loss of food quality that results from elevated temperatures. The electrical discharge method, alternatively named non-thermal plasma method, is investigated as one of the opportunities. Fast rising high voltage pulses have been applied to a corona electrode geometry producing filamentary, fast propagating discharges, called streamers. The energy per pulse is kept very low in order to prevent the thermal arcing phase. The presented research activities are directed to a better control and understanding of the discharge for a range of conditions (electrical, electrode geometry, process conditions). Different pulse shapes and treatment chambers have been applied to achieve a uniform treatment of continuous liquid flow. The paper presents a parameter study of the electrical circuit, simulated electrical field conditions and microbiological test results. A 6 log inactivation of Lactobacillus Plantarum in a 0,1 S/m phosphate buffer with pH = 5.5, has been demonstrated under continuous flow conditions with 14 degrees temperature increase. However, the inactivation of spores (Bacillus subtilis) after treatment in the discharge chamber, has not been observed.