Sub-lethal damage in Cronobacter sakazakii subsp sakazakii cells after different pulsed electric field treatments in infant formula milk

A study was carried out to study the possible cell damage caused by Pulsed Electric Field (PEF) to Cronobacter sakazakii subsp. sakazakii suspended in different commercial Infant Formula Milk (IFM) after different treatment conditions (15 and 35 kV/cm) associated with a minimum, medium and maximum energy input values. Post-treatment, the growth of survivors and the possible presence, recovery or death of sub-lethaly damaged cells was studied under refrigerated storage (8 degrees C) period of 24 h. A higher proportion of damaged cells were found at treatment conditions at which C. sakazakii shows higher resistance. PEF damaged a large proportion (80-90%) of C. sakazakii cells which then became sensitive to subsequent refrigerated storage in IFM. The greatest C. sakazakii reduction of 2.30 log cycles was achieved after 15 kV/cm-3000 mu s PEF treatment followed by 24 h refrigerated storage (8 degrees C), primarily due to PEF but also the formation and subsequent death of damaged cells followed by 24 h refrigerated storage (8 degrees C) period, with consequent IFM safety applicability. (c) 2009 Elsevier Ltd. All rights reserved.