In this paper the effect of microorganism size and shape on the killing efficiency of pulsed electric field (PEF) is investigated both experimentally and using a transient finite element program. The effect of cell size, membrane thickness, cell shape (spherical, elliptical, and cylindrical) on the calculated transmembrane voltage is studied. It has been found that both the cell size and cell membrane thickness have significant effect on the induced field across the cell membrane. The findings of the simulation results have been evaluated by comparing the trends with some experimental results. Five different types of microorganisms that have different shapes and dimensions have been inoculated with water at a conductivity level of 100 μS/cm and have been treated with the application of a pulsed electric field of 70 kV/cm. Significant difference in bacteria reduction was noticed between the treated cells which could be attributed to the cell size and shape.
The use of pulsed electric field (PEF) is considered as one of the most promising nonthermal food treatment methods. One of the design challenges in applying PEF technology is the design of the treatment chamber. In this paper, the effect of using multiple treatment zones on both the pulse shape and killing efficiency of PEF technology is addressed. With the increase in treatment zones, the loading effects and, hence, the circuit impedance changes result in changing both the pulsewidth and pulse shape. The changes have resulted in generating simple exponentially decaying pulses to oscillatory pulses, with significant reduction in pulsewidths. On the other hand, the increase in treatment zones also results in increased number of pulses applied as the liquid flows through different zones. It is therefore important to investigate the effects of treatment chamber impedance characteristics on PEF treatment performance, considering different liquids with a wide range of conductivity.Index Terms-Food processing, nonthermal pasteurization, pulsed electric field (PEF).
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