Inactivation of Escherichia coli by combining pH, ionic strength and pulsed electric fields hurdles

The use of pulsed electric fields is reported as a nonthermal process in the inactivation of bacteria and yeast. The inactivation of microorganisms is caused mainly by an increase in their membrane permeability due to compression and poration. Up to 2.2 log reductions in plate counts are observed when both pH and electric field are modified: pH from 6.8 to 5.7 and electric field from 20 to 55 kV/cm. Similar results are obtained when the ionic strength is reduced from 168 mM to 28 mM. The electric field and ionic strength are more likely related to the poration rate and physical damage of the cell membranes, while pH is more likely related to changes in the cytoplasmic conditions due to the osmotic imbalance caused by the poration. In this context, pulsed electric fields can be considered a hurdle which, combined with additional parameters such as pH, ionic strength, temperature and antimicrobial agents, can be effectively used in the inactivation of microorganisms. Copyright (C) 1996 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology