Inactivation of E. coli in Milk Tea Undergoing Pulsed Electric Field Pasteurization
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The aim of this study was to investigate the feasibility, design and construct a microorganisms inactivation system by pulsed electric field for industrial beverage pasteurization processes. The microorganism inactivation system consists of the DC pulsed high voltage power supply, the treatment chamber and the fluid flow system. The system is operated by using a pump to recirculate the beverage from the product tank into the coaxial treatment chamber of which the inner electrode is supplied with the DC pulsed voltage while the outer electrode is grounded in order to create the high pulsed electric field strength (20 kV/cm) inside this chamber. This electric field brings about the inactivation of microorganisms in the beverage inside the chamber by electroporation process. After the inactivation process, the treated beverage is pumped into the storage tank. In this study, the developed system was tested for the efficiency of E. coli inactivation with milk tea in a continuous recirculation system through liquid diet inactivation chamber. It was shown that the higher pulsed electric field and higher number of pulses resulted in higher inactivation efficiency. Increase in the flow rate of the milk tea resulted in the decrease in the inactivation efficiency. After the treatment, the milk tea temperature increased by about 2 - 3°C. Finally, the reduction of E. coli in the milk tea was found to be about 1.64 log CFU/mL with the treatment time of 30 min.
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