# Effect of PEF Treatment on Chosen Properties of Raw and Hot Air- and Freeze-Dried Poultry Meat
## 3 Results and Discussion
### The Influence of PEF Pretreatment on the Structure of the Hot Air- and Freeze-Dried Poultry Meat
#### 3.3.2 Rehydration Rate  
Due to the removal of water, the structure of dried material differs significantly from the structure of fresh raw material. The scale of changes depends on the drying method used, the applied process parameters, and the individual characteristics of the matrix [55; 63; 64; 65]. Rehydration and hygroscopic properties are among the features of dry products. They concern the ability to absorb and adsorb water, respectively [66].  
Figure 4 shows the rehydration rate (RR) and soluble solids loss (SSL) of the untreated and PEF-treated (15 and 30 kJ/kg) poultry meat dried using the hot air- and freeze-dried methods. As can be seen from Figure 4, in most of the analyzed cases, the amount of absorbed water increased with the passage of rehydration time. The FD poultry meat samples exhibited significantly higher RR values than the HA-dried poultry meat samples. Unlike the FD samples, a clear maximum RR is visible for the HA samples, which was reached after 90 min. The trends obtained for the FD samples depend on the analyzed process time--after 15 min, a higher RR was recorded for the untreated FD samples. In comparison, after 30 min, the PEF-pretreated FD samples showed a higher value of this parameter. In turn, the untreated HA samples showed a higher RR than the PEF-pretreated HA samples at each analyzed process time. It was also observed that the more water absorbed by the sample, the higher the SSL (Figure 4), which results from the leaching phenomenon occurring during rehydration [63]. In the case of the SSL, it was observed that after 30 min of the rehydration process, the soluble solid loss was significantly higher for the FD samples than for the HA-dried meat (Table 3). The poultry meat dried by FD had more than twice the SSL of the poultry meat dried with the usage of hot air (Table 3). Such a situation was connected with the high porosity of the FD samples and the easier leaking of compounds from the meat structure compared to the HA-dried meat. In addition, the one-way analysis of variance showed no significant differences in the SSL (after 30 min) between the untreated and PEF-pretreated dried samples.  
The poultry meat dried by FD had an RR that was more than twice as high (after 30 min of the process) as that of the poultry meat dried using HA (Table 3). The structure of the FD samples was much more porous than the structure of the HA samples (see Figure 3), which results in their higher ability to rebind water. Also, [PERSON] et al. [21] and  
Figure 4: Effect of PEF treatment (15 and 30 kJ/kg) of poultry meat dried with hot air (HA) and freeze-drying (FD) on (**a**) rehydration rate (RR) and (**b**) soluble solids loss (SSL).  
[PERSON] et al. [67] noted a higher RR of meat samples dried by freeze-drying than those dried with the usage of hot air. The performed one-way analysis of variance showed no significant differences in RR after 30 min of the process between the untreated and PEF-pretreated dried samples (\(p>0.05\)). Despite the lack of statistically significant differences, a slightly lower value of this parameter can be observed for the PEF-pretreated HA samples compared to the untreated samples dried in the same way. Additionally, the more energy supplied during the PEF pretreatment, the lower the RR. It can be concluded that as the degree of damage to the material tissue, as a result of electroporation, increased, the scale of irreversible structural changes also rose, which prevented the rebinding of water during rehydration [68].