# Processing Fresh-Cut Potatoes Using Non-Thermal Technologies and Edible Coatings
## 5 Emerging Processing Technologies: Operating Principles and Examined Parameters
### Olmic Heating (OH)  
The principle of this technique is based on electrical current passing through a conductive food--i.e., a food that contains a substantial amount of water, ions, or other polar compounds--allowing electricity to flow effectively. Fresh-cut potatoes, for instance, are well-suited for OH due to their high water content and natural salts, which facilitate conductivity [125]. As a result, the ions contained in the aqueous phase and salts of the food0 move to the electrodes of opposite charges [95]. Then, the energy generated due to the electrical resistance of the food leads to a rapid and uniform temperature increase (volumetric heating) [158]. The OH process is mostly affected by the electrical conductivity (EC) of the sample, which increases in the presence of ionic (polar) compounds such as acids, bases, and salts [95]. In contrast, non-polar molecules such as fats and oils do not affect the EC of the food product [95]. [PERSON]'s law defines the passage of electrical current (voltage) through the food sample according to the following equation [95]: \(V=I\times R\), where \(V\) is the voltage (V), \(I\) is the current intensity (A), and \(R\) is the resistance (\(\Omega\) or Ohm). The main parts of an ohmic heating system are a power source of alternating (AC) or direct current (DC), a non-electroconductive heating chamber (cell), stainless-steel electrodes, a thermocouple, a voltage control unit (current sensor), and a data monitoring and acquisition system (data logger and personal computer) [114]. The heating cell (chamber) can be in the form of a rectangle or cylinder [159, 160]. To increase the electrical conductivity of the food sample, the sample chamber is filled with water or salt solution [159]. The advantages of OH processing include rapid heating and a uniform temperature profile, reduced energy usage and high energy conversion efficiency, low maintenance cost, high retention of nutrients and bioactive compounds in the final dried food, and shorter heating times compared to traditional heating techniques, which give the treated samples an equivalent or longer shelf life [114, 160]. Specifically, the energy consumption of OH has been estimated to be 4.3-5.6 times lower than that of conventional heating [95]. OH can be applied as a pretreatment for solid food drying. In an industrial setting, OH is suitable for pretreating fresh-cut potatoes by inactivating browning enzymes, which helps prevent discoloration. This method is particularly useful for potatoes that will undergo further processing, like frying or baking. The disadvantages of OH are the corrosion of electrodes in ohmic cells due to electrochemical reactions, contamination of food by metals, low efficiency in food containing fat granules, higher initial cost to establish an OH system than conventional heating processes, and problems in upscale adaption [95, 159]. So far, OH has mainly been applied to liquid products such as fruit juices, aiming for juice concentration and resulting in a higher polyphenic content than after traditional heating [95, 160]. The non-thermal effects of OH treatment refer only to the inactivation of metal-containing enzymes such as PPO (Cu), lipoxygenase (Fe), and alkaline phosphatase (Zn and Mg) [114]. Slices of purple-fleshed potato (PFP) subjected to OH at a voltage of 40 V/cm for 4 min were found to contain more anthocyanin and total phenolics than the control samples [159]. In addition, the ascorbic acid content decreased when the voltage gradient was 20 V/cm and the duration increased from 2 to 4 min [159]. In another case, OH with a moderate electric field (15 and 30 V/cm) was applied at various temperatures and times to extract phytochemicals (anthocyanins and phenolic compounds) from the purple potato cultivar Vitelotte [161]. In brief, OH gave promising results as a green extraction method for industrial applications, avoiding organic solvents.