Assessment of pressure-induced inactivation of Listeria monocytogenes exposed to low pHs

摘要

This study was designed to evaluate the morphological and physiological characteristics of high pressure (HP)-treated Listeria monocytogenes treated at different pHs. L. monocytogenes in phosphate buffered saline (PBS, pH 7.2) adjusted with HCl or lactic acid to pH 4.0, 5.0, and 6.0 was subjected to 300 MPa for 5 min. The numbers of HP-treated L. monocytogenes at pH 4.0 adjusted with HCl or lactic acid were reduced by more than 6 log CFU/mL, while the numbers of non-HP-treated L. monocytogenes were not significantly reduced at pH 4.0. The propidium iodide (PI) fluorescence intensity of HP-treated cells adjusted with lactic acid was increased from 65 (pH 6.0) to 78% (pH 4.0). The HP-induced inactivation of L. monocytogenes in low pH was not directly associated with the membrane disruption. The results provide valuable information for understanding the HP-induced inactivation mechanisms and enhancing microbial lethality in acidic food systems.