Inactivation of Enterobacter sakazakii by pulsed electric field in buffered peptone water and infant formula milk

The effect of high-intensity pulsed electric field (PEF) treatment on the survival of Enterobacter sakazakii suspended in buffered peptone water (BPW) and powdered infant formula milk (IFM) was evaluated. Reference medium and IFM samples were treated with PEF. Electric field intensity and treatment time were varied from 10 to 40kVcm(-1) and from 60 to 3895 mu s, respectively. Samples of buffered peptone water (3gL(-1)) and IFM were inoculated with E. sakazakii(CECT858) (10(9)cfumL(-1)) and then treated with PEF. The inactivation data were adjusted to the Weibull frequency distribution function and Bigelow model, and constants were calculated for both substrates. A maximum 2.7log (cfu mL(-1)) reduction was achieved in BPW after exposure of E sakazakii to PEF for 360 mu s (2.5 mu s pulse width) at 40kVcm(-1). In IFM, exposure of E sakazakii to PEF, with the same conditions, led to a 1.2 log (cfumL(-1)) reduction. The greater the field strength and treatment time, the greater the inactivation achieved in both substrates. Even though further research will be necessary, according to the results, there are good prospects for the use of PEF in hospitals to achieve safe reconstituted infant formula before storage at refrigerated temperatures. (C) 2007 Elsevier Ltd. All rights reserved.