Pressure-induced inactivation of bacteria through pressure-assisted thawing using a thermal buffer zone.

•To maintain Isothermal conditions in samples, it was necessary to use thermal buffer.•Pressure-assisted thawing with thermal buffer achieved high levels of microbial inactivation; around 6-log reduction.•High inactivation rates took place at the thermal plateau under constant pressure.•The longer the thermal plateau, the higher the level of microbial inactivation.

Effect of thermal buffer zone was examined on the microbial inactivation through a pressure-assisted thawing. A plastic bag of bacterial suspension enclosed with a thermal buffer zone was frozen at − 50 °C, and treated for 20 min with a pressure-assisted thawing in water of 4 °C. A reduction of 8-log cycle was obtained at 200 MPa for the stationary growth phase cells of Escherichia coli that was suspended in 1% skim milk and enclosed with wheat flour/water paste and two polytetrafluoroethylene plates. When 100% ethanol was used as a thermal buffer and the samples were pressured at 194 MPa in 1% skim milk, levels of E. coli and Listeria monocytogenes were reduced by 6-log cycle and 7-log cycle, respectively. Staphylococcus aureus decreased by 4-log cycle.Industrial relevanceThis work will contribute to new developments in the pressure processing of foods, since the use of a thermal buffer zone in pressure-assisted thawing was very effective in enhancing the level of pressure-induced microbial inactivation.