## 3 Results and Discussion
### The Influence of US or PEF Pretreatment on the Sugar Content  
During osmotic dehydration, immersing the material in a hypertonic solution leads to the simultaneous movement of water from the material into the osmotic solution and the infusion of osmotic solutes in the reverse direction, from the osmotic solution into the material [45]. Figure 7 presents the content of sugars (sucrose, glucose, and fructose) in fresh and osmotically dehydrated strawberries (untreated and treated with US or PEF). Fresh strawberries contained 8.1 \(\pm\) 0.6 g sucrose in 100 g d.m., 15.8 \(\pm\) 0.7 g glucose in 100 g d.m., and 16.8 \(\pm\) 1.6 g fructose in 100 g d.m. Osmotic dehydration led to an increase in the sucrose content in strawberries by 394.1%, as well as a reduction in their glucose and fructose contents by 16.5 and 23.2%, respectively (untreated samples--SA_2). All three of the above-mentioned sugars are soluble sugars that naturally occur in strawberries [74]. Dehydration of these types of fruit in a sucrose solution resulted in a leakage of some of the glucose and fructose, while enriching them with the sucrose in which they were immersed [75]. The sucrose content in the untreated and in the US-pretreated osmotically dehydrated strawberries was similar. In turn, the PEF-pretreated and osmo-dehydrated samples had a significantly higher content of this sugar than the untreated osmo-dehydrated ones. The samples treated with US also had a similar glucose content to the untreated samples, while those samples treated with a PEF had the lowest content of this sugar. Although no statistically significant differences were observed in the fructose content among all dehydrated strawberries, a slightly lower concentration of this sugar was noted in the samples that underwent the PEF treatment. The highest changes in terms of sugar content in the PEF-pretreated and osmotically dehydrated strawberries could be caused by electroporation, which results in increased tissue permeability [76]. This led to the highest water loss (perhaps together with the glucose and fructose dissolved in it) (Figure 1b) and the highest solid gain (after sucrose penetration from the solution) of these samples (Figure 1c). As explained [PERSON] et al. [77] water removal and sugar gain in the case of mango subjected to the PEF treatment (1 kV/cm, 10 and 30 pulse numbers) and to osmotic dehydration (4 h, 40 \({}^{\circ}\)C, 60 \({}^{\circ}\)Brix agave syrup with or without addition of inulin or xanthan gum) depends on the plant tissue microstructure and its changes during the processing.  
Figure 7: Sugar content (sucrose, glucose, fructose) in osmotic dehydrated strawberries with the use of US and PEF treatments; SA: osmotic dehydrated strawberries in 50% sucrose solution; SA_PEF1 and SA_PEF2: pulsed electric field-treated strawberries with the energy of 1 or 2.5 kJ/kg and subjected to osmotic dehydration; SA_US1 and SA_US2: ultrasound-treated strawberries for 30 and 90 s and subjected to osmotic dehydration. The same letters (a–c for sucrose, A–D for glucose, a\({}^{\prime}\)–b\({}^{\prime}\) for fructose) at the columns present homogenous groups at \(\alpha=0.05\).