PEF, a novel non-thermal processing technology, which started to be applied to liquid food processing, has the potential to be used effectively in extracting useful ingredients from microorganisms, plant cells and animal cells. Unlike heat treatment, PEF treatment can preserve the natural favor, nutrients and functions of liquid foods such as fruit juice, vegetable juice and milk. Thus, it is regarded as a technology that corresponds to the increasing demand for fresh food.
During PEF treatment, high electric field (of 10~50kV/cm with a pulse duration of 1~100㎲) is applied to the target liquid. Then, the biological cells under the PEF undergo electroporation, which makes holes in the cell membrane. As a result, the intracellular contents leak and therefore the cells die off. This is the very principle of pasteurization or extraction methods.
PEF chambers have three main kinds―parallel-plate, co-axial, and co-linear―and other kinds derived from them. Most continuous PEF systems use co-linear chamber. Its drawback, however, is the non-uniformity of processing parameters in the chamber. The non-uniformity of the electric field in the treatment chamber remarkably increases the temperature in the regions with electric field strength peaks, and the liquid food passing through this region is overheated, which produces undesirable results like quality degradation due to contamination and composition modification. On the other hand, the lower electric field could rather be responsible for under-processing and therefore increases energy consumption alone due to Joule heat.
Based on the analysis of the previous studies, Kim Jin Hak, a researcher at the Faculty of Physical Engineering, has proposed a co-linear treatment chamber with sub-electrodes to increase the uniformity of the electric field intensity distribution inside the treatment chamber and to increase the volume of the treatment chamber, and investigated the effect of the sub-electrodes on the uniformity of electric field, the average electric field strength and the throughput of chamber.
The simulations and experiments have shown that the improved treatment chamber with sub-electrodes can produce more uniform fields in the treatment space, not only to ensure the uniformity of treatment but also to increase the throughput and reduce power consumption.
For more information, please refer to his paper “Improvement in uniformity of co-linear pulsed electric field treatment chamber by sub-electrodes and its optimization” in “Journal of Food Process Engineering” (SCI).
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