## 3 Results and Discussion
### Thermal Properties of Electrospun Pectin-Based Fibers  
The DSC curves corresponding to the cooling and second heating steps of the as-received PEO\({}_{2000}\) and pectin powders and the electrospun pectin-based fibers obtained from S3 and S5-S10 are gathered in Figure 2. During the cooling process, shown in Figure 2a, one can observe that PEO\({}_{2000}\) crystallized from the melt showing a crystallization temperature (T\({}_{\mathrm{c}}\)) of approximately 40 \({}^{\circ}\)C [61]. Alternatively, the pectin powder showed no crystallization during cooling in the whole tested thermal range. The crystallization peak attributed to PEO\({}_{2000}\) was not observed in the electrospun PEO\({}_{2000}\)-containing pectin fibers due to its relative low content. However, a small exothermic peak was observed at approximately 23 \({}^{\circ}\)C for the electrospun pectin fibers obtained from S10, which can be attributed to the crystallization of the PEG\({}_{900}\) confined in the carbohydrate [61; 62]. In Figure 2b one can observe the melting temperature (T\({}_{\text{m}}\)) of PEO\({}_{2000}\) at nearly 68 \({}^{\circ}\)C and also two low-intense melting peaks corresponding to the melting of the PEG\({}_{900}\) fraction in the pectin fibers obtained from S10 at approximately 24 \({}^{\circ}\)C and 40 \({}^{\circ}\)C [62]. Pectin did not exhibit any thermal transition of first order, that is, crystallization or melting, thus confirming the carbohydrate is fully amorphous [13; 63]. Moreover, no glass transition was observed up to nearly 230 \({}^{\circ}\)C, temperature from which the carbohydrate started thermal degradation. Previous studies on the thermal properties of pectin reported that thermal degradation of this carbohydrate is an exothermic process [63; 64]. It is worthy to note that the degradation temperature (T\({}_{\text{deg}}\)) of pectin shifted from 232 \({}^{\circ}\)C, for the neat powder, to 236 \({}^{\circ}\)C, for the electrospun fibers obtained from S10, which suggests that the thermal stability of the carbohydrate was slightly enhanced by the addition of PEG\({}_{900}\). This improvement can be related to the newly formed intermolecular PEG-pectin H-bonds and covalent esters, which delayed the thermal degradation of the pectin macromolecule [29]. Figure 2: Differential scanning calorimetry (DSC) curves of polyethylene oxide 2000 (PEO\({}_{2000}\)) powder, pectin powder, and electrospun pectin-based fibers during: (**a**) cooling and (**b**) second heating. The TGA curves of the neat pectin and PEO\({}_{2000}\) powders as well as the electrospun pectin-based fibers obtained from S3 and S5-S10 are shown in Figure 3. The most relevant thermal parameters obtained from the TGA curves are given in Table 3. One can notice that pectin exhibited three significant main weight losses, occurring at approximately 100 \({}^{\circ}\)C, 217 \({}^{\circ}\)C, and 240 \({}^{\circ}\)C. The first mass loss, which took place in the 75-110 \({}^{\circ}\)C range, can be ascribed to the removal of bound water from the carbohydrate due to its highly hydrophilic nature. In this regard, [PERSON] et al. [65] indicated that water evaporation of pectin observed between 50 \({}^{\circ}\)C and 150 \({}^{\circ}\)C, with a maximum at 100 \({}^{\circ}\)C, is identical to the dehydration process of other polysaccharides. [PERSON] et al. [66] and [PERSON] et al. [67] also observed a second weight loss between 195-350 \({}^{\circ}\)C. According to their studies, pectin shows a two-step degradation process in this range that might be related to the cracking of bonds or functional groups, structural depolymerization, and chain breaking of the polysaccharide.