Engineering of operation condition in milk pasteurization with PEF treatment

Abstract

We propose a new continuous pasteurization technique for milk that involves pulsed electric field (PEF) treatment with a voltage of 40 kVp and a frequency of 100 Hz. Escherichia coli with an initial concentration 107 cells/mL that was suspended in commercial milk was used as the target microorganism. Without control of the milk temperature, an average holding time in PEF treatment of 20 s should be necessary for the efficient inactivation of E. coli suspended in milk. Thermal control was incorporated in our system to improve the productivity and stability of the pasteurization process. Sufficient inactivation of E. coli cells was found to be possible even with an average holding time in PEF treatment of 10 s at a milk temperature of 50 °C or higher. We proposed a system for the PEF pasteurization of milk, in which a preheating unit and postholding unit were incorporated. When the milk temperature at the inlet of the PEF treatment chamber was controlled at 60 °C using preheating unit and the milk temperature after the PEF treatment was held at 70 °C for 20 s using the postholding unit, a reduction in the CFU of E. coli cells suspended in milk of at least seven orders of magnitude was achieved in our continuous PEF inactivation system.