Pathogen inactivation by pulsed electric fields - a survey of processing conditions, equipment design and potential applications for heat sensitive products.
Special Symposium - Innovations in Food Technology (LMC Congress)
Hygiene, Hygienic Design & Unit Operations (Food-5a)
Keywords: Pulsed Electric Field, Inactivation, Non-thermal, Minimal Processing, Energy Efficiency
The application of an external electric field can induce formation of pores in biological membranes, leading to a loss of semipermeability, leaking of intracellular content and loss of vitality. This effect can be utilized in food process engineering to improve mass transfer across cell membranes as well as for a gentle inactivation of micro-organisms in pumpable liquid media.
Our work is focussed on improving treatment efficiency in terms of costs of operation and treatment homogeneity to ensure product safety. Making use of synergetic effects of mild heat on PEF efficacy a drastic reduction of costs of operation can be obtained. Inactivation of L. monocytogenes, Staphylococcus, Campylobachter jejuni, Enterobacter sakazakii and Salmonella sp. in milk and other liquid media was investigated. The impact of electric field strength (10–40 kV/cm), temperature (20–55°C) and specific energy input (10–200 kJ/kg) on treatment efficacy has been evaluated. Dependent on treatment intensity up to 7-log reduction in microbial count were observed.
A model was developed to simulate a temperature-time profile during the PEF treatment as well as the thermal sensitivity of the microorganisms based on kinetic studies. A comparison of the thermal exposure during the PEF treatment and the thermal inactivation was used to distinguish between PEF and thermal effects. It was shown that a PEF treatment in combination with mild heat provides a potential to reduce the thermal load and retain native product properties of sensitive media. In addition a reduction of thermal load could be used to increase operating time of heat exchangers by reducing the amount of biofouling. As the PEF effect on enzymes and presumably other proteins remained small its application could be used to reduce the microbial count in nutrient broth, highly valuable ingredient solutions or milk for production of raw-milk-type cheese varieties.
A first commercial application of PEF technology for food preservation has been achieved in the US for premium fruit juices in a scale of 200 l/h in 2005. At the German Institute of Food Technology a technical scale unit has been developed, the feasibility of PEF preservation in industrial scale, equipment design and costs of the treatment will be discussed.
Presented Thursday 20, 09:20 to 09:35, in session Hygiene, Hygienic Design & Unit Operations (Food-5a).
