## 3 Results and Discussion
### Film-Forming Process of Electrospun Pectin-Based Fibers  
The electrospun mats of pectin fibers were subjected to annealing in order to eliminate or minimize the porosity and then produce homogenous and continuous films. Based on the DSC results shown above, pure pectin is fully amorphous. Therefore, a heat treatment in a wide range of temperatures, that is, 50-220 \({}^{\circ}\)C, was needed to be applied for different processing times, that is, from 5s to 120 s, to find out the best conditions. Figure 4 shows the visual aspect of the different electrospun films obtained after annealing and Figure 5 includes the SEM micrographs of their surface fracture. However, one can observe that, at any of these conditions, the annealing failed to provide homogenous films using the fibers obtained from the non-plasticized pectin solution, that is, from S3. Moreover, the color of films became darker when subjected to temperatures above 160 \({}^{\circ}\)C due to the low onset temperature of degradation of pectin fibers, which is shown above in Table 3. As seen in Figure 4a,b, by increasing the temperature or time, not only the pectin materials developed a dark color but also the fiber mats lost their integrity. Therefore, based on these results, one can consider that the non-plasticized pectin-based \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **T\({}_{\text{onset}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{deg1}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{deg2}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{deg3}}\) (\({}^{\circ}\)C)** & **Residual** \\  & & & & & & **Mass (\%)** \\ \hline Pectin powder & 98.0 \(\pm\) 5.2 \({}^{\text{a}}\) & 217.4 \(\pm\) 3.2 \({}^{\text{a}}\) & 240.2 \(\pm\) 2.1 \({}^{\text{a}}\) & - & 27.4 \(\pm\) 3.2 \({}^{\text{a}}\) \\ PEO\({}_{2000}\) powder & 375.3 \(\pm\) 2.4 \({}^{\text{b}}\) & - & - & 400.0 \(\pm\) 2.1 \({}^{\text{a}}\) & 23.7 \(\pm\) 1.2 \({}^{\text{b}}\) \\ Fibers from S3 & 175.4 \(\pm\) 2.5 \({}^{\text{c}}\) & 230.5 \(\pm\) 3.2 \({}^{\text{b}}\) & - & 367.5 \(\pm\) 3.2 \({}^{\text{b}}\) & 19.2 \(\pm\) 1.1 \({}^{\text{c}}\) \\ Fibers from S5 & 169.3 \(\pm\) 3.7 \({}^{\text{c,d}}\) & 230.3 \(\pm\) 3.1 \({}^{\text{b}}\) & 297.3 \(\pm\) 1.1 \({}^{\text{b}}\) & 367.3 \(\pm\) 2.1 \({}^{\text{b}}\) & 20.2 \(\pm\) 1.9 \({}^{\text{c}}\) \\ Fibers from S6 & 169.5 \(\pm\) 2.1 \({}^{\text{c,d}}\) & 229.8 \(\pm\) 2.0 \({}^{\text{b}}\) & 297.5 \(\pm\) 1.2 \({}^{\text{b}}\) & 367.1 \(\pm\) 2.0 \({}^{\text{b}}\) & 21.2 \(\pm\) 2.0 \({}^{\text{b,c}}\) \\ Fibers from S7 & 170.3 \(\pm\) 4.1 \({}^{\text{c,d}}\) & 227.5 \(\pm\) 2.1 \({}^{\text{b,c}}\) & 297.4 \(\pm\) 1.1 \({}^{\text{b}}\) & 367.3 \(\pm\) 3.2 \({}^{\text{b}}\) & 23.4 \(\pm\) 1.5 \({}^{\text{b}}\) \\ Fibers from S8 & 165.5 \(\pm\) 5.2 \({}^{\text{d}}\) & 226.4 \(\pm\) 2.2 \({}^{\text{c}}\) & - & 366.4 \(\pm\) 2.6 \({}^{\text{b}}\) & 21.2 \(\pm\) 1.3 \({}^{\text{b,c}}\) \\ Fibers from S9 & 168.2 \(\pm\) 4.4 \({}^{\text{d}}\) & 226.2 \(\pm\) 2.1 \({}^{\text{c}}\) & - & 367.4 \(\pm\) 3.1 \({}^{\text{b}}\) & 20.0 \(\pm\) 1.6 \({}^{\text{c}}\) \\ Fibers from S10 & 173.6 \(\pm\) 5.0 \({}^{\text{c,d}}\) & 227.2 \(\pm\) 3.0 \({}^{\text{b,c}}\) & - & 369.5 \(\pm\) 2.0 \({}^{\text{b}}\) & 17.3 \(\pm\) 1.2 \({}^{\text{d}}\) \\ \hline \hline \end{tabular} a \({}^{\text{a}-d}\) Different letters in the same column indicate a significant difference among the samples (\(p<0.05\)).  
\end{table} 
Table 3: Main thermal parameters of the neat pectin powder, PEO\({}_{2000}\) powder, and the electrospun pectin-based fibers in terms of: onset temperature of degradation (T\({}_{\text{onset}}\)), degradation temperature (T\({}_{\text{deg}}\)), and residual mass at 700 \({}^{\circ}\)C.  
fibers were too rigid to gain flexibility by the only application of heat. Therefore, pressure was also applied during annealing to promote fibers rearrangement and the removal of porosity.