## 3 Results and Discussion
### The Influence of US or PEF Pretreatment on the Physical Properties (Color, Texture)
[63] found that the firmness of osmotically dehydrated samples surpassed the corresponding values of freshly cut pumpkin samples. [PERSON] et al. [64] observed a decrease in the hardness of PEF-treated (1.2 kV/cm, 350 us) strawberry halves (1200 V/cm; 350 us) followed by osmotic dehydration for 4 h in sucrose and NaCl solution. According to [PERSON] et al. [65], PEF processing (25 \({}^{\circ}\)C, pulse width of 100 \(\upmu\)s, 0.1-0.4 kV/cm) used as pretreatment to osmotic dehydration (120 min) caused a significant decrease in the hardness of osmotically dehydrated strawberries depending on the applied electric field (0.1-0.4 kV/cm). This could be attributed to cellular rupture and the the creation of pores that led to the softening of the samples. Toward the end of the osmotic dehydration process, a minor increase in firmness was observed due to the substantial uptake of solids. This distinction arises from the fact that textural properties of fruit tissue are related to the cell wall component, influenced by sample size, shape, compression speed, and extent of compression [66]. The Influence of US or PEF Pretreatment on the Bioactive Compounds (TPC, TAC, Vitamin C, Antioxidant Activity--AA)  
During osmotic dehydration, the material is immersed in a specific osmotic solution. Depending on the purposed quality of the final product, it can be, e.g., starch, sucrose, glucose, fructose or corn syrup. The way in which this process is carried out permits the transfer of certain substances from the material to the osmotic solution, as well as in the reverse direction [67]. Figure 6 displays the total polyphenols content (TPC), the  
Figure 5: Maximum force (**a**) and work (**b**) necessary to deform strawberries subjected to US and PEF treatments and osmotic dehydration in 50% sucrose solution at 30 \({}^{\circ}\)C; 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 above the columns present homogenous groups at \(\alpha\) = 0.05.  
total anthocyanin content (TAC), the vitamin C content, and the antioxidant activity of fresh and osmotically dehydrated strawberries (untreated and treated with US or PEF). Fresh strawberries had the highest content of bioactive compounds--2981.0 \(\pm\) 34.0 mg chl. acid/100 g d.m. (TPC), 13.6 \(\pm\) 1.2 mg Cyd-3-glu/g d.m. (TAC), 122.7 \(\pm\) 9.4 mg ascorbic acid/100 g d.m. (vitamin C), 39.9 \(\pm\) 1.6 mg TE/g d.m. (DPPH), and 34.5 \(\pm\) 1.6 mg TE/g d.m. (ABTS). Osmotic dehydration has led to a reduction in the amount of these compounds in strawberries by 36.5, 31.7, 28.0, 42.2, and 31.9%, respectively (untreated samples--SA_2). The root cause of this observation can be found in the way the process was carried out. Not only water but also some of the bioactive ingredients dissolved in it could have penetrated the solution surrounding the material [67; 68]. As shown in Figure 6a, osmotically dehydrated strawberries pretreated with US exhibited significantly higher TPC than the untreated samples (SA_2). Cavitation, which is the basic mechanism of an ultrasound, produces significant shear force capable of breaking covalent bonds. As a result, antioxidant compounds may be released, e.g., phenols, flavones, carotenoids, or ascorbate [69; 70]. Despite the lack of statistically significant differences, a slightly higher retention of polyphenols has also been observed in samples treated with PEF (in comparison to untreated samples). The effect of PEF on enzyme activity is still unclear. In the analyzed case, this non-thermal technique could reduce the activity of an enzyme involved in the oxidation of substances containing polyphenol groups--polyphenol oxidase. This would justify the higher TPC in the PEF-treated samples [67].