## 3 Results and Discussion  
The Influence of US or PEF Pretreatment on the Kinetics of the Strawberry Osmotic Dehydration Process  
The time-dependent behavior of the osmotic dehydration process for strawberries was analyzed. This analysis considered scenarios with no pretreatment, as well as those involving ultrasound or PEF pretreatments. The evaluation involved parameters like mass loss, water loss, and solid gain (Figure 1). The most intensive mass transfer was observed during the first 30 min regardless of the pretreatment used. [PERSON] et al. [11], who conducted osmotic dehydration of kiwi fruit with or without ultrasound-assisted osmotic dehydration (40 kHz, 80 kHz, 40 + 80 kHz with intensity of 25 W/L, 50 W/L, 75 W/L), also observed that the highest mass transfer occurred in the early stage of the process. This trend was attributed to the initial stage of the process, where there exists a substantial osmotic pressure difference between the osmo-dehydrated material and the surrounding solution, and this difference gradually diminishes over time [45]. It was found that mass loss and water loss were highest in the case of using a PEF pretreatment with an energy of 2.5 kJ/kg, and then 1 kJ/kg, regardless of the osmotic dehydration time used. This is related to the mechanism of the PEF. The PEF causes electroporation of the plant tissue cell membrane, which leads to an increase in osmotic efficiency [46; 47; 48]. The effect of the PEF pretreatment on the enhancement of mass transfer during osmotic dehydration has been also observed in previous studies [16; 49; 50]. Furthermore, it is worth noting that the application of ultrasound, independently of its duration, resulted in less mass loss and water loss compared to a PEF treatment, but more than in the case of the no pretreatment samples. In might be explained by the mechanism of ultrasound, which consists in forming microscopic channels in the tissue, thus facilitating the removal of moisture [45]. The mass loss is a consequence of a bigger flow of water from the raw material than the solids flow penetrating plant tissue during osmotic dehydration [51]. Water loss increased with the duration of the osmotic dehydration process in all analyzed materials. At the end of the osmotic dehydration process (after 2 h), it was found that the highest water loss occurred in the material subjected to osmotic dehydration using a PEF pretreatment of 2.5 kJ/kg. Regardless of the pretreatment used, the highest water losses were recorded in the initial stage of osmotic dehydration. As the osmotic dehydration process continued, the rate of water loss gradually diminished. After the initial stage, in which the diffusion process is rapid, the rate of change of water loss decreases [52]. Therefore, [PERSON] et al. [53] found that the use of ultrasound for 10 min is useful for water removal only for short osmotic dehydration processes (120 min, 25 \({}^{\circ}\)C, 61.5% sucrose solution). In turn, [PERSON] et al. [54] performed an osmotic dehydration on potatoes (30-70% of osmotic solution concentration, 32.5-45 \({}^{\circ}\)C, 0-180 min) and showed that the application of ultrasound (5 min of US treatment, 32.5 \({}^{\circ}\)C, 40% of amplitude level, 7/6 pulse duration/pulse interval ratio) increased in the first 60 min of water loss, and that the solid gain obtained the same or even better osmotic effect as the normal osmotic dehydration over a long time (180 min). Their study showed that ultrasound-assisted osmotic dehydration lasting a short time (\(\sim\)60 min) had the same effect as longer osmotic dehydration without an ultrasound application, and the difference in water loss between treatments was most intense during the first hour.