Pressurized and unpressurized samples were 10-fold serial diluted (10-1e10-8) in sterile Ringer Solution (Merck KGaA, Ger-
many). One millilitre of each dilution was pour-plated in triplicate in Plate Count Agar (PCA) medium (Liofilchem, Italy). After incu-
bation (37 oC/48 h) the number of colonies was counted in the most
suitable dilutions. The survivor number was reported as log CFU ml-1 and values were used to determine high pressure reduction effectiveness (RE), using the equation RE ¼ log N0 - log N, where N0
and N represent, respectively, the number of viable cells in the unpressurized suspensions and in the pressurized suspensions.
Institute of High Pressure Physics, Poland) and the pressurization fluid was a mixture (60:40) of water and propylene glycol (DOW- CAL™, Dow). Non-pressurized controls were also included for each strain in the different experiments.