_Article_  
Analytical and Experimental Studies on the  
Application of a Series of Treatment Chambers for  
_Escherichia coli_ Inactivation by Pulsed Electric Fields  
[PERSON] 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30  
breakdown of the microbial membrane, not for generating heat. With optimal pulse parameters (time, frequency, etc. ), it is possible to control the increase in the temperature of the treated samples, thus limiting the influences of the treatment on the nutritional contents, appearance, and taste of the food product. Even though the PEF technique for food pasteurization has been proposed for more than 50 years, there are still issues needed that to be clarified for the use of PEF in practice. This is due to the fact that there is a variation in the types of microorganisms and in the natures of food materials, which need different treatment conditions for the PEF treatment. Moreover, the treatment chamber or actuator design, electrode geometries, electric pulse characteristics, electric field intensity, and other process factors also affect the treatment efficiency for the specific microbial inactivation of liquid foods [2; 3; 7; 11; 13; 14; 15]. Generally, the PEF technique requires a very short pulse width (1-100 microseconds), with magnitudes in the range of 5-50 kV/cm. The treatment should operate with a short residence time (lower than 1 s) at a 20-60 \({}^{\circ}\)C liquid food temperature to allow efficient microorganism inactivation with a high level of food safety [2; 7; 13; 16]. However, the disadvantage of current PEF technology in static liquid treatment is the requirement of considerable operation energy, because a large treatment system is usually used to reduce the operating time for liquid replacement. In this type of the treatment process, a liquid medium is usually stored in a large treatment chamber, and time-consumingly treated with a very high pulsed voltage, dependent on the size and distance of electrodes, to satisfy the electroporation criteria for microbial inactivation [2; 7; 17; 18; 19]. Therefore, the requirement of an expensive pulsed voltage generator is unavoidable. The possibility of solving this problem would be an application of the PEF treatment with a flow-through system [3; 4; 13; 14; 17; 20; 21; 22; 23; 24; 25]. In this type of treatment system, the PEF treatment chamber could be in-line equipped in the liquid food production line. Therefore, the PEF chamber size, the magnitude of the pulsed voltage generation, and the time and energy consumption could be decreased. However, the design of the PEF treatment chamber including the treatment parameters is rather complicated. Most of these PEF treatment types require a re-circulation pumping system for the re-treatment process to improve the inactivation efficiency. Therefore, the issue of time consumption is still incompletely resolved. Recently, the flow-through liquid treatment chamber has been focused on due to the aforementioned advantages. The treatment chambers have been developed into several configurations, such as parallel, coaxial, and co-field or co-linear treatment chambers [14; 20; 22; 25; 26; 27]. However, the co-field treatment chamber seems to have preferable geometry. The co-field treatment chamber is composed of two hollow electrodes separated by an insulator. In this chamber configuration, the electric field distribution is not highly uniform due to the interface between the electrode and insulator. The PEF systems could be operated at lower power in comparison with the static treatment system [22; 28; 29]. The insulator profile can significantly reduce the maximum field at the interface between the electrode and insulator, resulting in joule heating reduction. It should be noted that during the PEF processes, joule heating is unavoidable since electric current passes through a conductive liquid food. The heat may affect the quality of the treated food.