Nasiłowska Justyna, Kocot Aleksandra, Osuchowska Paulina Natalia, Sokołowska Barbara
Wacław Dąbrowski Institute of Agricultural and Food Biotechnology-State Research Institute, 01-142 Warsaw, Poland.
Department of Immunology and Food Microbiology, Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences, 10-748 Olsztyn, Poland.
Foods. 2021 Nov 30;10(12):2940. doi: 10.3390/foods10122940.
High Hydrostatic Pressure (HHP) technology is considered an alternative method of food preservation. Nevertheless, the current dogma is that HHP might be insufficient to preserve food lastingly against some pathogens. Incompletely damaged cells can resuscitate under favorable conditions, and they may proliferate in food during storage. This study was undertaken to characterize the extent of sublethal injuries induced by HHP (300-500 MPa) on and strains. The morphological changes were evaluated using microscopy methods such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Epifluorescence Microscopy (EFM). The overall assessment of the physiological state of tested bacteria through TEM and SEM showed that the action of pressure on the structure of the bacterial membrane was almost minor or unnoticeable, beyond the wild-type strain. However, alterations were observed in subcellular structures such as the cytoplasm and nucleoid for both and strains. More significant changes after the HHP of internal structures were reported in the case of wild-type strains isolated from raw juice. Extreme condensation of the cytoplasm was observed, while the outline of cells was intact. The percentage ratio between alive and injured cells in the population was assessed by fluorescent microscopy. The results of HHP-treated samples showed a heterogeneous population, and red cell aggregates were observed. The percentage ratio of live and dead cells (L/D) in the collection strain population was higher than in the case of the wild-type strain (69%/31% and 55%/45%, respectively). In turn, populations were characterized with a similar L/D ratio. Half of the cells in the populations were distinguished as visibly fluorescing red. The results obtained in this study confirmed sublethal HHP reaction on pathogens cells.
高静水压（HHP）技术被认为是一种食品保鲜的替代方法。然而，目前的主流观点是，HHP可能不足以持久地保存食品以抵御某些病原体。未完全受损的细胞在有利条件下可以复苏，并且它们可能在储存期间在食品中增殖。本研究旨在表征HHP（300 - 500 MPa）对[具体菌株1]和[具体菌株2]菌株造成的亚致死损伤程度。使用扫描电子显微镜（SEM）、透射电子显微镜（TEM）和落射荧光显微镜（EFM）等显微镜方法评估形态变化。通过TEM和SEM对受试细菌生理状态的总体评估表明，除了[具体野生型菌株]外，压力对细菌膜结构的作用几乎很小或不明显。然而，在[具体菌株1]和[具体菌株2]菌株的亚细胞结构如细胞质和类核中均观察到了变化。对于从生汁中分离出的野生型菌株，HHP处理后内部结构发生了更显著的变化。观察到细胞质极度浓缩，而细胞轮廓完整。通过荧光显微镜评估群体中活细胞和受损细胞之间的百分比比例。HHP处理样品的结果显示群体异质性，并且观察到红细胞聚集体。[具体菌株1]收集菌株群体中的活细胞与死细胞百分比比例（L/D）高于野生型菌株（分别为69%/31%和55%/45%）。反过来，[具体菌株2]群体具有相似的L/D比例。群体中一半的细胞被区分为明显发出红色荧光。本研究获得的结果证实了HHP对病原体细胞的亚致死反应。
