High intensity pulsed electric fields applied for food preservation

Preservation of liquid foods by high intensity pulsed electric fields (PEF) is an interesting alternative to traditional techniques like thermal pasteurization. Based on the underlying mechanism of action, in this paper the crucial process parameters electrical field strength, total pulse energy input and treatment temperature were investigated experimentally. Inactivation studies were performed with three bacteria (E. coli, Bacillus megaterium, Listeria innocua) and one yeast (Saccharomyces cerevisiae). Stainless steel and carbon electrodes have been tested to investigate their applicability as electrode material. Simulating the influence of cell size and orientation as well as the presence of agglomerations or insulating particles indicated that the applied field strength has to be increased above the critical one to achieve product safety. It was found that temperatures higher than 40 °C can strongly increase the lethality of the PEF process. In this way also small cells like Listeria are easily affected by pulsed fields even at a field strength as low as 16 kV cm−1. In addition, heating of the product prior to PEF has the advantage that most of the required process energy can be recovered using heat exchangers. Exemplary, such a process is analyzed by an enthalpy balance.