## 3 Results and Discussion
### Effect of the Pre-Treatment on the Properties of Dried Material
The increased density was a result of the decreased volume of the slices and increased shrinkage, along with the prolongation of the processing time and the application of US. The increase in shrinkage, as a result of ultrasound treatment prior to drying, was also noted by [PERSON] et al. [25]. Similarly, [PERSON] et al. [13] noticed increase in shrinkage for apples immersed in ethanol before drying. On the other hand, [PERSON] et al. [49] reported a reduction in shrinkage after treatment with ethyl alcohol in the case of apples. However, it should be mentioned that the treatment was carried out under different conditions, hence probably different trends. Rehydration ability is an important physical property of dried products, as the amount of water absorbed by dried material may affect the textural and visual properties [11,18,49]. A good rehydration capacity is especially important in the case of dried carrot tissue, due to its further use in, e.g., soups. In conducted research, the dried untreated material was characterized by a rehydration rate equal to 5.35 \(\pm\) 0.07 (Table 4). EtOH treatment, especially when it was combined with US, resulted in increased rehydration capacity, which was in the range of 5.27-6.01 for EtOH (increase of up to 12%) and from 5.99 to 6.37 for EtOH+US (increase of up to 19%). It was proven that type of treatment significantly influenced (\(p\) < 0.05, Table 4) the rehydration ability, which was probably related to the increased porosity of the material as a result of damage to the internal structure during sonication [30]. This means that the use of treatment in ethanol, especially when this treatment is supported by the ultrasound, increases the possibility of re-absorption of water of dried carrots. [PERSON] et al. [49] came to similar conclusions that the pre-treatment in ethanol improved the rehydration properties and porosity of dehydrated apples. The authors explained the higher rehydration capacity of apples treated with ethanol by changes in the microstructure, including thinned cell walls, which swelled upon rehydration. The same results were obtained for rehydrated pumpkin [18], carrot [11] and scallion stalk [26] when the material was treated by ethanol with and without sonication. These changes were explained by the better access of the ethanol molecules into the tissue, which improved the resistance of plant cells to shrinkage during the drying. It could be noticed that in most cases the material subjected to ethanol with US assistance showed worse hygroscopic properties, which could be due to increased damage of the structure. On the basis of the presented results, it can be concluded that with the selected parameters of the pre-treatment, it is possible to influence the hygroscopic properties of dried products. Reduced water vapour adsorption may increase the storage stability of dried material. Table 5 shows the colour parameters of dried carrots, which were subjected to pre-treatment in ethanol (EtOH) and ethanol-ultrasound (EtOH+US21). Dried carrot slices, untreated before drying, had an L* value equal to 51.5 \(\pm\) 4 and after the immersion treatment in ethyl alcohol (EtOH), darkening of the dried carrots was observed. Whereas, the sonication assistance did not significantly change the lightness of dried material in comparison to the untreated dried carrot. The different effect of both treatments, with and without ultrasound assistance, was confirmed by the two-way analysis of variance (\(p\) < 0.05, Table 5). However, the treatment time did not have a significant effect (\(p\) > 0.05, Table 5). [PERSON] and [PERSON] [2] noted that the sonication parameters influenced both the darkening of dried sonicated carrots, as well as causing no changes in carrot colour, compared to those not pre-treated. The lack of changes in the lightness of dried carrots treated with ethanol and ultrasound means that there is a positive effect of this type of treatment on the colour of dried carrots.