# Processing Fresh-Cut Potatoes Using Non-Thermal Technologies and Edible Coatings
## 5 Emerging Processing Technologies: Operating Principles and Examined Parameters
### Osmotic Dehydration (OD)  
This process is based on the immersion (dipping) of a solid food in a hypertonic (highly concentrated) solution [6]. As a result, the food loses water, and the osmo-active solute is transferred into the food [36; 118]. Hence, OD is a counter-current mass transfer process, the optimization of which depends on the cellular foodstuff and the operating conditions [119]. The diffusion of the solute compound into the product depends on the food tissue (structure), immersion time, solution temperature, concentration, and agitation (or stirring) [120]. However, the critical concentration of the osmotic agent should be taken into account, since below this concentration, the fresh-cut food can uptake water instead of dewatering [6]. The optimal result of OD treatment is to maximize water loss (g/100 g fresh sample) and minimize solid gain (g/100 g fresh sample) [17; 119]. The first parameter reflects the dehydration extent, whereas the second one indicates the dry solids (salt or sugar) diffused from the osmotic solution into the potato. In addition, the lower the solid gain, the healthier the processed potato [14]. Generally, water loss and solid gain increase with increasing immersion time. The initial rate of salt uptake by potato cubes was found to increase with increasing NaCl concentration (10-18% \(w/w\)) in the osmotic solution, whereas the water loss increased with temperature (20-55 \({}^{\circ}\)C) and NaCl concentration (10-18% \(w/w\)) [121]. OD offers significant energy and quality advantages since it operates at lower temperatures (30-50 \({}^{\circ}\)C) than conventional, vacuum, or hot air drying methods, reducing the risk of heat-induced quality degradation [36]. Unlike high-energy processes like freeze-drying (lyophilization), OD requires less energy, making it a more economical and environmentally sustainable choice [10; 121]. Low temperatures in OD also help prevent structural damage to cell membranes and reduce the loss of volatile flavor compounds, preserving the sensory quality of the fresh-cut food [36]. In an industrial setting, OD can be used to pretreat fresh-cut potatoes to lower the water content, which helps reduce microbial growth and extend shelf life, making it particularly valuable for potatoes destined for drying or frying applications. However, a key disadvantage of OD is the management of spent osmotic solution, which needs proper disposal or valorization; a common approach is its reuse in beverage production [36]. According to the reviewed papers presented in Table 3, the most commonly employed osmotic agents used in fresh-cut potato processing are sodium chloride and sucrose. In a few studies, these agents were used simultaneously [119; 122] or in combination with maltodextrin [6; 7] and grape seed extract [118]. Other studies used only maltodextrin [123] or ethanol [124]. Higher water loss and shorter drying times were observed at higher ethanol concentrations [124]. It should be noted that ethanol used at a relatively high concentration (30% \(w/v\)) in the aforementioned study is considered a higher-cost liquid compared to other osmotic agents in Table 3. Generally, the concentration of sucrose (up to 50-70%) used in osmotic solution was higher than that of NaCl (up to 30%) (Table 3). The immersion time in NaCl or sucrose solutions usually varied from 1 to 3 h (Table 3). On the other hand, different potato-to-osmotic-solution ratios were used in the studies listed in Table 3. Some works suggested ratios >1:10 in order to avoid dilution during treatment and operational cost [122]. The immersion of fresh potatoes in NaCl solutions was also tested in pre-cut (unpeeled) potato tubers in order to investigate its influence on browning, PPO activity, and amino acid content [9]. In another study, a novel variant of OD in NaCl or sucrose solutions, called post-dipping dehydration, was used, with a short immersion time of 1.5 min [14]. As a result of short immersion, the dipped potato slices gained a lower amount of sugar or salt.