Inactivation of Escherichia coli O157:H7 and Salmonella enteritidis in liquid egg white using pulsed electric field

The effects of temperature and pulsed electric field (PEF) intensity on inactivation of pathogens such as Escherichia coli O157:H7 and Salmonella enteritidis in egg white was investigated. Liquid egg white inoculated with 10(8) colony-forming units (CFU)/mL of each pathogen was treated with up to 60 pulses (each of 2 mu s width) at electric field intensities of 20 and 30 kV/cm. The processing temperatures were 10 degrees C, 20 degrees C, and 30 degrees C. After treatment, uninjured and total viable cells were enumerated in selective and nonselective agars, respectively Maximum inactivations of 3.7 and 2.9 log units were obtained for S. enteritidis and E. coli O157:H7, respectively, while injured cells accounted for 0.5 and 0.9 logs for E. coli O157:H7 and S. enteritidis, respectively For both bacteria, increasing treatment temperature tended to increase the inactivation rate. There was synergy between electric field intensity and processing temperature. The inactivation rate constant k(T) values for E. coli O157:H7 on both selective and nonselective agars were 8.2 x 10(-3) and 6.6 x 10(-3)/mu s, whereas the values for S. enteritidis were 16.2 x 10(-3) and 12.6 x 10(-3)/mu s, respectively The results suggest that E. coli O157:H7 was more resistant to heat-PEF treatment compared with S. enteritidis.