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 μs, the time interval between the pulses was varied from 4 μs 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. The results showed that the decontamination rate increased logarithmically from a value, which was obtained with two independent pulses to 1.5 times this value for pulses separated by 4 μs. The average repair time of the E. coli bacteria after electric shocks, defined as the time for which the difference in survival rate for closely spaced (4 μs) and widely separated (40 s) pulses had increased to 50% of its maximum value, is approximately 10 ms. This result is not only of scientific interest, but it shows that it is possible to increase the energy efficiency of bacterial decontamination using pulsed electric fields by more than 25 percent using reprated systems with repetition rates exceeding 100 Hz.
|Journal||IEEE International Conference on Plasma Science|
|State||Published - 2001|
|Event||28th IEEE International Conference on Plasma Science/ 13th IEEE International Pulsed Power Conference - Las Vegas, NV, United States|
Duration: Jun 17 2001 → Jun 22 2001