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

LWT ◽  
2006 ◽  
Vol 39 (4) ◽  
pp. 420-426 ◽  
Author(s):  
M.I. Bazhal ◽  
M.O. Ngadi ◽  
G.S.V. Raghavan ◽  
J.P. Smith
Author(s):  
Malek Amiali ◽  
Michael Ngadi ◽  
James P. Smith ◽  
Vijaya Raghavan

This study sought to evaluate the effect of PEF parameters such as electric field intensity and number of pulses on the inactivation of Escherichia coli O157:H7 and Salmonella Enteritidis suspended in liquid whole egg. The medium was inoculated with 108 CFU ml-1 of E. coli O157:H7 or S. Enteritidis and was treated continuously at 10, 20 or 30°C using electric field intensity of either 20 or 30 kV cm-1. A biphasic instant reversal PEF waveform with up to 105 pulses of 2 µs in width was applied. Bacterial inactivation increased with increasing applied electric field intensity, number of pulses and processing temperature. Maximum reductions of 3.9 and 3.6 log cycles were obtained for E. coli O157:H7 and S. Enteritidis, respectively. The maximum input energies required to inactivate E. coli O157:H7 and S. Enteritidis were 538 and 914 J, respectively. The higher kinetic value was obtained for S. Enteritidis (0.043 µs-1) representing the more heat–PEF sensitive bacteria compared to E. coli O157:H7.


2001 ◽  
Vol 64 (6) ◽  
pp. 777-782 ◽  
Author(s):  
RAGIP UNAL ◽  
JIN-GAB KIM ◽  
AHMED E. YOUSEF

Pulsed electric field (PEF) and ozone technologies are nonthermal processing methods with potential applications in the food industry. This research was performed to explore the potential synergy between ozone and PEF treatments against selected foodborne bacteria. Cells of Lactobacillus leichmannii ATCC 4797, Escherichia coli O157:H7 ATCC 35150, and Listeria monocytogenes Scott A were suspended in 0.1% NaCl and treated with ozone, PEF, and ozone plus PEF. Cells were treated with 0.25 to 1.00 μg of ozone per ml of cell suspension, PEF at 10 to 30 kV/cm, and selected combinations of ozone and PEF. Synergy between ozone and PEF varied with the treatment level and the bacterium treated. L. leichmannii treated with PEF (20 kV/cm) after exposure to 0.75 and 1.00 μg/ml of ozone was inactivated by 7.1 and 7.2 log10 CFU/ml, respectively; however, ozone at 0.75 and 1.00 μg/ml and PEF at 20 kV/cm inactivated 2.2, 3.6, and 1.3 log10 CFU/ml, respectively. Similarly, ozone at 0.5 and 0.75 μg/ml inactivated 0.5 and 1.8 log10 CFU/ml of E. coli, PEF at 15 kV/cm inactivated 1.8 log10 CFU/ml, and ozone at 0.5 and 0.75 μg/ml followed by PEF (15 kV/cm) inactivated 2.9 and 3.6 log10 CFU/ml, respectively. Populations of L. monocytogenes decreased 0.1, 0.5, 3.0, 3.9, and 0.8 log10 CFU/ml when treated with 0.25, 0.5, 0.75, and 1.0 μg/ml of ozone and PEF (15 kV/cm), respectively; however, when the bacterium was treated with 15 kV/cm, after exposure to 0.25, 0.5, and 0.75 μg/ml of ozone, 1.7, 2.0, and 3.9 log10 CFU/ml were killed, respectively. In conclusion, exposure of L. leichmannii, E. coli, and L. monocytogenes to ozone followed by the PEF treatment showed a synergistic bactericidal effect. This synergy was most apparent with mild doses of ozone against L. leichmannii.


2004 ◽  
Vol 24 (1) ◽  
pp. 71-85 ◽  
Author(s):  
N. HERMAWAN ◽  
G. AKDEMIR EVRENDILEK ◽  
W.R. DANTZER ◽  
Q.H. ZHANG ◽  
E.R. RICHTER

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