Influence of Pulse Rise Time on the Inactivation of Staphylococcus Aureus by Pulsed Electric Fields

In this paper, the effect of rise time (200 ns and 2 μs, respectively) of rectangular pulse on the inactivation of Staphylococcus aureus has been studied. Apple juice with three different conductivities (1.5 mS/cm, 2.0 mS/cm, and 2.5 mS/cm) was inactivated 75 μs at an electric field strength of 25 kV/cm, 30 kV/cm, and 35 kV/cm, respectively. The experiment results showed that the pulse with shorter rise time had higher effect of inactivation and lower solution temperature increases after treatment, and the difference between te inactivation effects was more than 0.5 logs in general. Fast Fourier transform analysis showed that the pulse with shorter rise time had higher amplitude of low frequencies and more high-frequency components, which resulted in a higher transmembrane potential of Staphylococcus aureus cells and higher effect on intracellular material.