Microbial species and strain heterogeneity affect resistance to high pressure processing

Ten strains of each of Listeria monocytogenes (BHI 200, 300 and 400 MPa, 10 min, 20 °C) to investigate the impact of species and strain variability in piezotolerance. L. monocytogenes was the most resistant, followed by E. coli, L. plantarum and S. cerevisiae. L. monocytogenes L6 was the most robust and NCTC 10357 the most sensitive strain, while overall survival was better in TSB-D (no glucose) than in BHI (naturally contains glucose) under similar pressures. Strains ranked differently according to their piezotolerance in the two media, while this was serotype-dependent in TSB-D. E. coli strain variability was detected under all conditions with O157 VT- and FAM 21843 as most robust and most sensitive respectively. L. plantarum FBR04 and ATCC14917 were the most resistant and sensitive (300 MPa), respectively, while for S. cerevisiae this corresponded to AD1890 and 028.0315 (200 MPa). This study confirms the importance of species and strain variability in HHP. The results are relevant for the improvement of decontamination efficiency predictions, the design of validation studies and the application of hurdle technology. Knowledge of microbial inactivation and strain variability under mild HHP conditions can allow fine-tuning of hurdle technology and lead to production of safer, more affordable HHP-treated food due to decrease of operating costs.