Hiperbaric, S.A., Department of Applications and Food Processing, C/ Condado de Treviño, 6, 09001 Burgos, Spain; University of Burgos, Department of Biotechnology and Food Science, Faculty of Sciences, Pza. Misael Bañuelos s/n, 09001 Burgos, Spain.
Hiperbaric USA Corporation, Department of Applications and Food Processing, 2250 NW 84(th) Avenue, 101, Miami, FL 33122, United States.
Food Res Int. 2021 Feb;140:110091. doi: 10.1016/j.foodres.2020.110091. Epub 2021 Jan 5.
Despite the commercial success of high pressure processing (HPP) in the juice industry, some regulatory agencies still require process validation. However, there is a lack of consensus on various aspects regarding validation protocols, including the selection of representative strains to be used in challenge tests. This study characterized the variable response of Escherichia coli O157:H7 (34 strains), Listeria monocytogenes (44 strains) and Salmonella enterica (45 strains) to HPP, and identified potential candidates to use in process validation. Stationary phase cells were submitted to 500 MPa for 1 min at 10 °C in model solutions consisting of tryptic soy broth + 0.6% yeast extract (TSBYE) adjusted to pH 4.5 and 6.0 with citric acid. At pH 6.0, pressure resistance widely varied between species and within strains of the same species. E. coli O157:H7 and L. monocytogenes were the most pressure resistant and showed high variability at strain level, as the total count range given by minimum and maximum counts spread between 2.0 and 6.5 log CFU/ml. S. enterica was the least resistant pathogen with more than 82% of the isolates displaying non-detectable counts after HPP. Recovery through storage at 12 °C was also variable for all pathogens, but eventually most strains recovered with median counts on day 14 between 8.3 and 8.9 log CFU/ml. For pH 4.5 solutions, 26 E. coli O157:H7 strains displayed survivors after HPP but did not adapt, registering non-detectable counts in the next sampling dates. None of the L. monocytogenes and S. enterica strains survived HPP or incubation at pH 4.5 (<2.0 log CFU/ml), suggesting that citric acid at 4.16 g/l is a safe barrier for pathogen control under moderate HPP conditions. Principal component and cluster analyses served to propose strain cocktails for each species based on their pressure resistant and adaptation phenotypes. Additionally, S. enterica was identified as less pressure resistant and less prone to recover following HPP than E. coli O157:H7 and L. monocytogenes, so its relevance in process validation for juices should be questioned. Future work will validate the proposed strain cocktails on real food systems.
尽管高压处理（HPP）在果汁行业取得了商业成功，但一些监管机构仍要求进行工艺验证。然而，在验证协议的各个方面，包括选择用于挑战性测试的代表性菌株方面，尚未达成共识。本研究对大肠杆菌 O157:H7（34 株）、单核细胞增生李斯特菌（44 株）和肠炎沙门氏菌（45 株）对 HPP 的可变响应进行了表征，并确定了用于工艺验证的潜在候选菌株。将处于静止期的细胞在 pH 值为 4.5 和 6.0 的模型溶液中（由胰蛋白酶大豆肉汤+0.6%酵母提取物（TSBYE）组成，并使用柠檬酸调节），在 10°C 下用 500 MPa 处理 1 分钟。在 pH 值 6.0 下，不同物种之间以及同一物种内的菌株之间的耐压性差异很大。大肠杆菌 O157:H7 和单核细胞增生李斯特菌是最耐压的，在菌株水平上表现出高度的变异性，因为最低和最高计数之间的总计数范围在 2.0 和 6.5 log CFU/ml 之间。肠炎沙门氏菌是最不耐压的病原体，超过 82%的分离株在 HPP 后显示无法检测到的计数。所有病原体在 12°C 下储存时的恢复情况也各不相同，但最终大多数菌株在第 14 天的中位计数在 8.3 到 8.9 log CFU/ml 之间。对于 pH 值为 4.5 的溶液，26 株大肠杆菌 O157:H7 株在 HPP 后显示出存活但未适应，在下一次采样日期显示无法检测到的计数。没有一株单核细胞增生李斯特菌和肠炎沙门氏菌在 HPP 或在 pH 值为 4.5 下孵育后存活（<2.0 log CFU/ml），这表明在适度 HPP 条件下，柠檬酸在 4.16 g/l 是控制病原体的安全屏障。主成分和聚类分析用于根据每种菌株的耐压性和适应性表型提出菌株混合物。此外，肠炎沙门氏菌被鉴定为比大肠杆菌 O157:H7 和单核细胞增生李斯特菌更不耐压，并且在 HPP 后更不易恢复，因此其在果汁工艺验证中的相关性值得怀疑。未来的工作将在实际食品系统上验证所提出的菌株混合物。
