Alvarez I, Pagán R, Raso J, Condón S
Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
Lett Appl Microbiol. 2002;35(6):489-93. doi: 10.1046/j.1472-765x.2002.01221.x.
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).
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.
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.
Erroneous conclusions and misinterpretation of results are possible if factors affecting the PEF resistance of L. monocytogenes are not considered during PEF inactivation studies.
研究处理培养基的生长阶段、生长温度、储存时间、pH值和水分活度对单核细胞增生李斯特菌对脉冲电场（PEF）抗性的影响。
使用频率为1 Hz、脉冲宽度为2 μs、场强为25和28 kV/cm的方波脉冲。在所研究的两个培养温度（4℃和35℃）下，细胞在稳定期比在对数期对PEF更具抗性。无论生长阶段如何，在4℃下生长的细胞比在35℃下生长的细胞对PEF更敏感。在25 kV/cm和800 μs处理后，在pH值7.0、5.4和3.8时分别获得了1.48、3.86和5.09个对数循环的失活。处理培养基水分活度的降低可保护细胞免受PEF处理。
单核细胞增生李斯特菌对PEF的抗性取决于不同的环境因素。应了解并控制生长条件和处理培养基特性的影响，以获得可重复和可靠的PEF失活数据。
如果在PEF失活研究中不考虑影响单核细胞增生李斯特菌对PEF抗性的因素，可能会得出错误的结论并对结果产生误解。
