Combined High Pressure and Subzero Temperature Phase Transition on the Inactivation of Escherichia coli ATCC 10536

Combined high pressure and subzero temperature phase transition was performed to inactivate Escherichia coli ATCC 10536 at 200 MPa. Inactivation was compared among atmospheric pressure inactivation (APFI), pressure assisted freezing inactivation (PAFI), pressure assisted thawing inactivation (PATI), and pressure shift freezing inactivation (PSFI). Phase transition characteristics of microbial suspension were concurrently analyzed to investigate its influence on microbial inactivation. Phase transition temperature of E. coli ATCC 10536 suspension decreased to -23.8 degrees C at 200 MPa, which is observed from the phase transition plateau. Supercooling was observed from nucleation temperature (-25 degrees C) of PAFI. PATI resulted in the most inactivation of 4.37 log reduction, followed by PAFI and PSFI in decreasing order. APFI showed no efficacy of inactivation for E. coli ATCC 10536. Synergistic effect of high pressure, subzero temperature, and phase transition was expected for microbial inactivation.