Environmental factors influencing the inactivation of Listeria monocytogenes by pulsed electric fields.
OBJECTIVE
To investigate the influence of the growth phase, growth temperature, storage time, pH and aw of the treatment medium on the resistance of Listeria monocytogenes to pulsed electric fields (PEF).


RESULTS
Square wave pulses of 2 micros at a frequency of 1 Hz and 25 and 28 kV cm(-1) were used. Cells were more PEF resistant in the stationary than in the exponential phase at both incubation temperatures investigated (4 and 35 degrees C). Cells grown at 4 degrees C were more PEF sensitive than cells grown at 35 degrees C independent of the growth phase. After a treatment of 25 kV cm(-1) and 800 micros, 1.48, 3.86 and 5.09 log10 cycles of inactivation were obtained at pH 7.0, 5.4 and 3.8, respectively. A reduction in the aw of the treatment medium protected cells against PEF treatments.


CONCLUSIONS
The PEF resistance of L. monocytogenes depended on different environmental factors. The influence of growth conditions and treatment medium characteristics should be known and controlled to obtain reproducible and reliable PEF inactivation data.


CONCLUSIONS
Erroneous conclusions and misinterpretation of results are possible if factors affecting the PEF resistance of L. monocytogenes are not considered during PEF inactivation studies.
Alvarez
I
I
Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
Pagán
R
R
Raso
J
J
Condón
S
S
D015169:Colony Count, Microbial; D003470:Culture Media; D004553:Electric Conductivity; D004558:Electric Stimulation; D005519:Food Preservation / Q000379:methods; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000254:growth & development*; D013696:Temperature
D003470:Culture Media