Reduction of Escherichia coli O157:H7 on goat meat surface with pulsed dc square wave signal

Pulsed dc square wave electric signal was applied to goat meat samples, inoculated with Escherichia coli O157:H7 on the surface, covered with a thin film of 0.15 M sodium chloride solution. Experiments were conducted with 10, 20 and 30 mA/cm2 current intensities for 2, 8 and 32 min of treatment durations. Effects of 100, 1 k and 10 kHz frequency signals were tested for the survival of E. coli with 20 mA/cm2 and 80% duty cycles. Three duty cycles of 30, 50 and 80% at 1 kHz frequency and 20 mA/cm2 were applied to test the inactivation rate of E. coli. The results indicated that all three intensities of current effectively inactivated E. coli cells at treatment duration of 32 min. Eight log10 reductions per ml of E. coli cells were achieved. A decrease in treatment duration decreased log10 reduction of E. coli. Frequencies of 1 kHz or more and duty cycles of 50% or more accelerated the inactivation of E. coli cells at 20 mA/cm2 current.