Repair time of bacteria after pulsed electric field application

Summary form only given. Pulsed electric fields are widely used for bacterial decontamination of water and liquid food The decontamination mechanism is assumed to be electroporation of the cell membrane. Depending on pulse amplitude and duration a certain percentage of the bacteria suffer irreversible damage, and consequently cell death. Those, which survive need a certain time to repair the field-induced damage. By applying two electric field pulses, and measuring the viability of the bacteria depending on the time between pulses, it is possible to obtain information on the repair-time. The pulses were generated by means of a generator with IGBTs as switches. The maximum voltage was 1.5 kV, at a maximum current of 160 A. The pulse duration of the square pulse (rise and fall time approximately 200 ns) was 4 /spl mu/s, the time interval between the pulses was varied from 4 /spl mu/s to 40 s. The load was a cuvette filled with broth, which contained the Escherichia coli bacteria. The viability of the E. coli after electric field application was measured by using manual counting for E. coli colonies in cultured agars.