# Processing Fresh-Cut Potatoes Using Non-Thermal Technologies and Edible Coatings
## 5 Emerging Processing Technologies: Operating Principles and Examined Parameters
### Pulsed Electric Field (PEF)  
The operating principle of PEF is the application of high voltage (0.1-80 kV/cm) and very short repetitive monopolar (unipolar) or bipolar pulses on vegetable and fruit tissues. The pulse duration (or width) varies from micro- (us) to milliseconds (ms). The shape of pulses can be square-wave [141], rectangular [142], or exponential [143]. The food sample is placed between two stainless-steel parallel electrodes within a treatment chamber, where high-voltage pulses are repeatedly applied [3]. Generally, a PEF system consists of three main parts: (i) high-voltage pulse generator, (ii) treatment chamber, and (iii) control-monitoring system [144]. Key process parameters are electric field strength, flow rate, pulse waveform (exponential, rectangular, square-wave), pulse repetition rate, exposure time (pulse duration), specific energy density, and temperature variation in the treated sample [144]. The treatment chamber can be filled with deionized or tap water, potato juice, or salt solution in order to improve the electrical conductivity between the immersed potato sample and the electrodes [145]. The size of the chamber and the adjustable distance between the electrodes depend on the sample size [142]. For example, lab-scale electrodes are reported to have a surface area in the order of 100-400 cm\({}^{2}\), dimensions of 20 mm \(\times\) 20 mm, and a thickness of 1 mm, respectively, whereas the distance between them (electrode gap) can vary from 1 to 80 cm [3]. According to the literature, the potato sample (slice, cube, cylinder, etc.) is placed parallel to the electrodes and is in contact with either the left or right electrode. Hence, the sample can exhibit a lengthwise orientation. In case of a cylindrical chamber (tube), electrodes are located at the bottom and top of the chamber [15]. As a low-cost alternative to high-intensity pulsed electric fields, low-density direct current (DC) electrical fields (40 V/cm for 1 min) were successfully used to reduce the browning of rehydrated, freeze-dried (lyophilized), non-blanched potato cylinders [96]. The input of electrical energy density (\(Q,J/m^{3}\)) supplied to the sample is calculated as follows:  
\[Q\,(J/m^{3})=V_{0}\times I\times t/\
u, \tag{1}\]  
where \(V_{0}\) is the peak voltage (V), \(I\) is the current intensity (A), \(t\) is the treatment time (s), and \(\
u\) is the volume of the treatment chamber (m\({}^{3}\)). The total treatment time (\(t_{\text{PEF}}\)) is calculated as follows [146]:  
\[t_{\text{PEF}}=N\times n\times\tau, \tag{2}\]  
\[T=n\times\tau, \tag{3}\]  
where \(N\) is the number of trains, \(n\) is the number of the pulses, and \(\tau\) is the duration of each pulse (us); T represents the total processing time. On the other hand, the specific energy input is calculated using the following equation [147]:  
\[W_{\text{specific}}\,(k)/kg)=(V^{2}\times n\times m)/(R\times W), \tag{4}\]  
where \(V\) is the pulse voltage (kV), \(n\) is the pulse number (dimensionless), \(m\) is the pulse width (us), \(R\) is the pulse resistance (ohm), and \(W\) is the total weight of the sample and processing liquid in the treatment chamber (g). The advantages and disadvantages of PEF are described in a recent publication [144]. One of the significant advantages of PEF lies in its ability to enhance microbial inactivation. The application of short, intense electric pulses to food products disrupts the cell membranes of microorganisms, leading to their deactivation [148]. This results in extended shelf life and improved safety of the treated food products. Additionally, PEF offers advantages in terms of maintaining the nutritional quality of foods. Unlike traditional thermal processing methods, PEF operates at lower temperatures, minimizing the impact on heat-sensitive nutrients and preserving the sensory attributes of the food [144]. Another notable advantage of PEF is its impact on enzymatic activity.