## 3 Results and Discussion
### Dried Juice and Pomace
#### 3.3.4. Hygroscopicity of Dried Juice and Pomace  
Hygroscopicity (H) is a parameter that indicates food stability, and is particularly important in the case of powders. It allows for determining the product's ability to absorb water from the environment, which is crucial with regard to changes in the powder's properties during storage and for the selection of appropriate packaging. Hygroscopic properties depend on the composition of the raw materials and, in the case of powders, also on the content and type of the carrier used [48]. In order to assess the hygroscopicity of the beetroot powders, they were stored in an environment with a water activity of 0.756 for 72 h. The powder that was produced using spray drying and not subjected to PEF pretreatment (DASDJC0) was characterized by an H of 26.5% (Figure 3). A similar H (27.4%) was noted for the powder pretreated with 3 electric pulses (DASDJC1). An increase in H (32.8%) was observed for the powder that was subjected to PEF pretreatment in the amount of 44 pulses (DASDJC2). After 72 h, the samples did not reach equilibrium water content, and their mass was constantly increasing. Therefore, it was noted that the more intensive PEF treatment of the beetroots that were used for juice production caused an increase in the H of the powders obtained by spray drying, which is not a favorable effect as it decreasesthe powders' storage stability. The greatest increase in powder mass was observed during the first 10 h of the experiment.  
In the case of the beetroot pomace that was freeze-dried, the H of the sample that was not treated with PEF reached 21.4% (FDP0). The pomace that was pretreated with three electric pulses was characterized by an H of 22.2% (FDP1), and the beetroots subjected to 44 electrical pulses (FDP2)--by an H of 26.2% (Figure 3). The pomace powders, similar to the spray-dried juices, absorbed water the fastest during the initial 10 h. The equilibrium moisture was not reached either, and their mass continued to increase.  
The water vapor sorption kinetics for the powdered freeze-dried beetroot pomace (FDP0, FDP1, FDP2) differed from the curves for the spray-dried juices. However, in both cases, the material subjected to the highest amount of electrical pulses (DASDJC2 and FDP2) absorbed significantly more water than the samples that were not pretreated (DASDJC0, FDP0) and those treated with only 3 pulses (DASDJC1, FDP1). These results correlate fairly well with [PERSON] et al. [49], where red bell pepper juice was spray-dried, and a lower H of powders was observed when 1 kJ/kg PEF was applied prior to pressing bell peppers in order to produce a liquid feed compared to the materials that were not treated or treated with a higher-intensity PEF (3 kJ/kg). [PERSON] et al. [50] freeze-dried apple tissue and observed a similar correlation regarding the H of samples. They noted a 4.5% higher H of the samples that were not pretreated with a PEF compared to the apples that were treated prior to freeze drying. It was concluded that this phenomenon was a consequence of electroporation that enhanced the soluble solids migration to the surface, which affected the H of dried samples. As expected, the results obtained in this research prove that PEF pretreatment can influence the hygroscopic properties and enhance the H of dried samples to some extent. However, it should be emphasized that it depends on the intensity of the PEF applied and the raw material type.