Synergistic effect of high pressure processing and Lactobacillus casei antimicrobial activity against pressure resistant Listeria monocytogenes

The purpose of this study was to evaluate combinations of high pressure processing (HPP) and Lactobacillus casei antimicrobial activity against Listeria monocytogenes strains with variation in pressure resistance in culture and in a food model. In culture, combination of HPP (350 MPa, for 1–20 min) and Lb. casei cell extract (CE, 32 CEAU/ml) showed a significant synergistic bactericidal effect (P < 0.05) and the combination treatment decreased pathogen's population >5 log10 CFU/ml. Synergy between CE and HPP was most evident in the pressure-resistant strain, OSY-8578. Similar result was observed in meat products where high pressure (500 MPa for 1 min), and high-activity CE (100 CEAU/g) caused >5 log reduction in the viability of L. monocytogenes Scott A. The combination treatment resulted in the absence of peaks associated with cellular components in DSC thermogram suggesting that the presence of CE may have caused a considerable damage to cellular components during the high pressure treatment.