Inactivation of Serratia liquefaciens on dry-cured ham by high pressure processing

To quantify the inactivation of Serratia liquefaciens exerted by high pressure processing (HPP), slices of dry-cured ham were inoculated and processed combining different levels of technological parameters: pressure (347-852 MPa), time (2.3-15.8 min) and temperature (7.6-24.4 °C) according to a central composite design. Bacterial inactivation, as logarithmic reduction, indicated that S. liquefaciens was relatively sensitive to HPP. Six log reductions were achieved in a total of 10 trials combining pressures of 600 MPa or above with different holding times and temperatures. The inactivation of S. liquefaciens was analysed through the multiple regression analysis to generate a second order polynomial equation. Pressure and time were the two factors which significantly determined the inactivation of S. liquefaciens on dry-cured ham. Temperature did not significantly affect the lethality of the process. The response surface methodology was used to determine optimum process conditions to maximize the inactivation of S. liquefaciens in the experimental range tested. The maximum inactivation of S. liquefaciens in dry-cured ham was achieved by combining a pressure of 650 MPa with a holding time of 8 min. Combinations above these values (i.e. 750 MPa for 13 min) would not significantly improve the lethality of the process.