Evaluation of the use of pulsed electrical field as a factor with antimicrobial activity

The aim of the work was to evaluate the optimal conditions to produce a significant reduction in bacteria population using pulsed electrical field (PEF). Bacteria strains of Escherichia coli, Acinetobacter lwoffii, Citrobacter freundii, Serratia liquefaciens, Pseudomonas aeruginosa, Staphylococcus gallinarum, Staphylococcus xylosus and Oligella sp. were isolated from the surface of egg shells and identified using ATB System (Merck). They were compared with ATCC strains of E coli, Staphylococcus aureus and P. aeruginosa. The research with PEF was conducted in two different diluting agents: physiological solution and egg white. A suspension containing 10(6) CFU/ml was prepared. Variations in number of bacteria cells in suspension, treated with pulsed electric field, were observed using 1-300 electrical impulses between 15, 20 and 25 kV, separated 1 s pulse period. The significant reduction in bacteria population was noted using 200 pulses and intensity of 25 kV. At the end of the process the number of cells was reduced in population by more than 3-5 log cycles, depending on bacteria. High inactivation levels obtained for some microorganisms suggest that PEF could assure a safe, high quality product with an extended shelf life what is especially important for egg products. Egg products processed by traditional heat treatments exhibit operational problems due to protein coagulation in heat exchangers. Using egg white as a high heat-sensitive material in experiment it was important to find optimal conditions of pasteurization without destructive changes in egg white proteins' activity. One of the main findings of the investigation was that the death of microbes was not associated with an increase in temperature; the temperature of sample subjected to electrical impulses was not higher than 47 degrees C after processing. The whipping properties of pasteurized white e.g. foaming ability and foam stability were investigated to check the condition of white. (c) 2006 Elsevier Ltd. All rights reserved.