Bacterial Injury Induced by High Hydrostatic Pressure

In food processing, high hydrostatic pressure (HHP) can inactivate microbes, and the inactivation is either lethal or sublethal, depending on the intensity of HHP-induced stress. Inactivation of bacteria is a key to ensure food safety by HHP food processing. This manuscript reviews HHP-induced injury of bacteria such as Escherichia coli, Listeria monocytogenes, and (vegetative) Bacillus subtilis. The stress in the sublethal inactivation depends on HHP level, holding time, bacterial species/strain, and other environmental factors. The sublethal inactivation induces injury of bacteria, and the injured bacteria may recover under suitable conditions. The recovery behavior depends on nutrients surrounding the bacteria and the storage temperature. In the detection of HHP-injured bacteria, detection media and incubation temperature play important roles. Mechanisms involved in HHP-injured bacteria can be discussed from several viewpoints including membrane damage, reactive oxygen species, HHP resistance, ribosomes, metabolome, and colony-forming behavior. HHP-induced injury of molds, yeasts, parasites, and viruses has not been sufficiently studied.