Inactivation of Escherichia coli O157:H7 in liquid whole egg using combined pulsed electric field and thermal treatments

Inactivation of Escherichia coli O157:H7 in liquid whole egg using thermal and pulsed electric field (PEF) batch treatments, alone and in combination with each other, was investigated. Electric field intensities in the range from 9 to 15 kV/cm were used in the study. The threshold temperature for thermal inactivation alone was 50 degrees C. PEF enhanced the inactivation of E. coli O157:H7 when the sample temperature was higher than the thermal threshold temperature. The maximum inactivation of E. coli O157:H7 obtained using thermal treatment alone was similar to 2 logs at 60 degrees C. However, combined heat and PEF treatments resulted in up to 4 log reduction of the pathogen. The kinetic rate constants k(TE) for combined treatments at 55 degrees C varied from 0.025 to 0.119 pulse 1 whereas the rate constants at 60 degrees C ranged from 0.034 to 0.228 pulse(-1). These results indicated a synergy between temperature and electric field on the inactivation of E. coli O157:H7 within a given temperature range. (C) 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.