## 3 Results and Discussion
### Thermal Properties of Electrospun Pectin-Based Fibers
The carbohydrate then lost 60% of its total weight up to 350 \({}^{\circ}\)C whereas, in the 350-697 \({}^{\circ}\)C range, the mass loss was 15% of its original weight and the maximum rate of weight loss was observed at 235 \({}^{\circ}\)C. During thermal degradation of pectin different depolymerization reactions occur, including demethylation, depolymerization by backbone hydrolysis and hydrolytic cleavage of neutral sugar side chains [66; 67; 68]. The most instable bonds, formed by the neutral sugars, thermally degrade first. The polygalacturonic acid units of high M\({}_{\text{W}}\) hydrolyze later whereas the glycoside bonds formed by uronic acids also degrade at higher temperatures. Depending on the pectin properties, that is, pH, source, degree and pattern of methyl esterification, acid hydrolysis or \(\beta\)-elimination reactions take place during the thermal degradation [69]. In particular, the here-used low methyl esterified amidated pectin results in acid hydrolysis reactions with the temperature increase [70; 71]. During hydrolysis, longer chains break up to the shorter as the cleavage of \(\alpha\)-(1,4)-glycosidic bond connecting two uronic acids by the addition of a water molecule [72]. In our study, above 250 \({}^{\circ}\)C, a secondary degradation of pectin has been reported to occur, including release of functional side groups and chains break, while gasification of char residues arises at temperatures around 600 \({}^{\circ}\)C [73]. Figure 3: Thermogravimetric analysis (TGA) curves of the neat pectin powder, PEO\({}_{2000}\) powder, and electrospun pectin-based fibers. Alternatively, it can be observed that PEO\({}_{2000}\) was highly thermally stable, showing the values of onset degradation temperature (T\({}_{\text{onset}}\)) and maximum degradation temperature (T\({}_{\text{deg}}\)) of approximately 375 \({}^{\circ}\)C and 400 \({}^{\circ}\)C, respectively. One can also observe that the incorporation of PEO\({}_{2000}\) successfully delayed the thermal degradation of pectin up to nearly 175 \({}^{\circ}\)C. The reason of this behavior can be explained by the occurrence of more chain entanglements and the newly formed intermolecular PEO-pectin H-bonds and covalent esters, leading to the formation of a more stable and less volatile material. The pectin-based fiber obtained from the electrospinningning of S3, S5, and S6 showed a similar thermal degradation profile than the neat pectin powder but with even lower values of T\({}_{\text{deg}}\). This result suggests that, even though PEO\({}_{2000}\) delays the onset of degradation of pectin, it also catalyzes its thermal degradation. Interestingly, the presence of both plasticizers contributed to increasing the thermal degradation of the PEO\({}_{2000}\)-containing pectin fibers. The pectin-based fibers obtained from the electrospinningning of S5-S10, which included glycerol or PEG\({}_{900}\), showed a similar thermal degradation profile in comparison with the PEO\({}_{2000}\)-containing pectin fibers but with slightly lower values of T\({}_{\text{onset}}\). Additionally, the new weight loss obtained nearly 290 \({}^{\circ}\)C can be attributed to glycerol degradation. One can then consider that the plasticizers played a role in the pectin chains motion that favored chain scission during thermal degradation. Similar results were found for chia mucilage-glycerol films in the study performed by [PERSON] et al. (2017), showing that the glycerol addition lowered the heat resistance of the carbohydrate. Moreover, lower residual masses were observed for the plasticizer-containing fibers compared with the non-plasticized fibers. This effect was particularly intense for the electrospun pectin fibers obtained from S10, that is, the solution containing 3 wt% PEG\({}_{900}\), which showed a residual mass of 17 wt%.