Principle of Pulsed Electric Field Technology
The basic principle of the PEF technology is the application of short pulses of high electric fields with duration of microseconds to milliseconds and intensity in the order of 10-80 kV/cm. The processing time is calculated by multiplying the number of pulses times with effective pulse duration. The process is based on pulsed electrical currents delivered to a product placed between a set of electrodes; the distance between electrodes is termed as the treatment gap of the PEF chamber. The applied high voltage results in an electric field that causes microbial inactivation (see Figure 18.104.22.168).
After the treatment, the food is packaged aseptically and stored under refrigeration. The treatment is applied to a food product held between two electrodes inside a
Figure 22.214.171.124 Flow chart of a PEF food-processing system with basic component (8).
chamber, usually at room temperature. Food is capable of transferring electricity because of the presence of several ions, giving the product in question a certain degree of electrical conductivity. So, when an electrical field is applied, electrical current flows into the liquid food and is transferred to each point in the liquid because of the charged molecules present (Qin et al., 1995).
PEF is able to inactivate microorganisms in the food, reduce enzymatic activity, and extend shelf- life with negligible changes in the quality of the final product as compared to the original one. According to the intensity of the field strength, electroporation can be either reversible (cell membrane discharge) or irreversible (cell membrane breakdown or lysis), but this effect can be controlled depending on the application (Ho and Mittal, 1996).
This process leads to dielectric breakdown of the microbial cell membranes and to interaction with the charged molecules of food (Fernandez-Diaz et al., 2000; Zimmermann, 1986). Hence, PEF technology has been suggested for the pasteurization of foods such as juices, milk, yogurt, soups, and liquid eggs (Vega-Mercado et al.,1997; Bendicho., 2003; Puertolas et al., 2004; Eissa, 2012).