91E-25 |
Determination of electrical properties of liquid foods exposed to pulsed electric fields |
M. AMIALI, M. O. Ngadi, and V. G. S. Raghavan. Agricultural and Biosystems Engineering, McGill University, Macdonald Campus, 21,111 Lakeshore Rd., Ste. Anne-de-Bellevue, QC H9X-3V9, Canada The use of Pulsed electric fields (PEF) is increasingly receiving attention as a non-thermal technology for pasteurizing liquid food products. The effectiveness of PEF treatment for a specific product depends on the product’s electrical properties such as electrical conductivity and specific resistance of the product in a given treatment chamber as well as the energy transferred to the product during the PEF process. The objectives of this study were to determine electrical properties of several liquid food products at different processing temperatures and to determine the energy transfer characteristics necessary to match treatment chamber to pulse generator. Liquid egg products, namely, egg white, yolk and whole liquid egg, and fruit juices including apple, orange and pineapple juices were selected for study. The PEF generator was a transmission line square wave instant charge reversal generator with a 100 W impedance. The electrical properties were measured at temperatures ranging from 5 to 55°C. Voltage and current across the treatment chamber were measured simultaneously during each electric field pulse. The electrical conductivity, specific resistance and energy transferred per pulse were calculated. The results showed that electric conductivity increased whereas the energy transferred and the specific resistance decreased with increasing temperatures for all products, except for apple juice for which the energy transferred reached a maximum at 35°C. Liquid egg products have the greatest overall electric conductivity, ranging from 0.22 to 1.1 S/m. Fruit juice products have the lowest electrical conductivity in the range from 0.13 to 0.63 S/m due to their low ionic concentrations. The energy transferred to the products decreased or increased depending on the cell treatment load resistance. These results indicate that the cell treatment resistance must be adequately matched to the PEF transmission line load (RL=RS) in order to transfer maximum electrical energy to the food product. In addition, the PEF system must be designed with the electrical properties database provided in this study in order to treat the liquid foods properly.
Session 91E, Nonthermal Processing: Nonthermal processing of foods
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