Mosqueda-Melgar Jonathan, Raybaudi-Massilia Rosa M, Martín-Belloso Olga
Department of Food Technology, University of Lleida, UTPV-CeRTA, Av. Alcalde Rovira Roure, 191, 25198 Lleida, Spain.
Int J Food Microbiol. 2007 Jun 30;117(2):192-200. doi: 10.1016/j.ijfoodmicro.2007.04.009. Epub 2007 Apr 25.
Consumption of unpasteurized melon and watermelon juices has caused several disease outbreaks by pathogenic microorganisms worldwide. Pulsed electric field (PEF) has been recognized as a technology that may inactivate those bacteria present in fluid food products at low temperatures. Hence, PEF treatment at 35 kV/cm, 4 mus pulse duration in bipolar mode and square shape were applied on Salmonella Enteritidis, E. coli and L. monocytogenes populations inoculated in melon and watermelon juices without exceeding 40 degrees C outlet temperatures. Different levels of treatment time and pulse frequency were applied to evaluate their effects on these microorganisms. Treatment time was more influential than pulse frequency (P</=0.05) on the PEF microbial reduction levels for both melon and watermelon juices. Populations of S. Enteritidis, E. coli and L. monocytogenes were experimentally reduced and validated in a single process up to 3.71+/-0.17, 3.7+/-0.3 and 3.56+/-0.26 log(10) units, respectively, in melon juice when 1440 micros and 217 Hz were used; whereas reductions up to 3.56+/-0.12, 3.6+/-0.4 and 3.41+/-0.13 log(10) units of those microorganisms, respectively, were reached in watermelon juice treated for 1727 micros at 188 Hz. Although PEF treatment reduced the populations of the three microorganisms, L. monocytogenes was more resistant to PEF than S. Enteritidis and E. coli in both juices when treated at the same processing conditions.
在全球范围内，食用未经巴氏杀菌的甜瓜汁和西瓜汁已导致多起因致病微生物引发的疾病暴发。脉冲电场（PEF）被认为是一种能够在低温下使液体食品中存在的细菌失活的技术。因此，在不超过40℃出口温度的情况下，对接种于甜瓜汁和西瓜汁中的肠炎沙门氏菌、大肠杆菌和单核细胞增生李斯特氏菌群体施加35 kV/cm、双极模式下4 μs脉冲持续时间且呈方形的PEF处理。应用不同水平的处理时间和脉冲频率来评估它们对这些微生物的影响。对于甜瓜汁和西瓜汁，处理时间对PEF微生物减少水平的影响比脉冲频率更大（P≤0.05）。当使用1440 μs和217 Hz时，在甜瓜汁中，肠炎沙门氏菌、大肠杆菌和单核细胞增生李斯特氏菌群体经实验分别减少并验证至3.71±0.17、3.7±0.3和3.56±0.26 log₁₀单位；而在188 Hz下处理1727 μs的西瓜汁中，这些微生物分别减少至3.56±0.12、3.6±0.4和3.41±0.13 log₁₀单位。尽管PEF处理减少了这三种微生物的群体数量，但在相同处理条件下处理时，在两种果汁中，单核细胞增生李斯特氏菌比肠炎沙门氏菌和大肠杆菌对PEF更具抗性。
