Inactivation of Escherichia coli cells with sonication, manosonication, thermosonication, and manothermosonication: Microbial responses and kinetics modeling

The responses of Escherichia coli K12 to sonication, manosonication (MS), thermosonication (TS), and manothermosonication (MTS) treatments were investigated at 40, 47, 54, and 61 °C and 100, 300, 400, and 500 kPa, in comparison with heat only treatments at the same temperatures. The inactivation kinetics were evaluated with five selected models and two statistical indices. Within the time frame (4 min) and temperature range used in this study, inactivation of E. coli K12 with a single lethal factor (heat or sonication) can be described by a first-order kinetic equation. For treatments with more than one lethal factor, non-linear inactivation curves were observed, which included a fast initial inactivation followed by a slow reduction in microbial survival counts. The biphasic model produced the best fit of the inactivation data compared to other non-linear models. Environmental scanning electron microscopy images showed extensive cell damage and breakage on E. coli K12 cells treated by MS, TS, and MTS.