## 3 Results and Discussion
### Rheological Testing
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**(b) Gelatin hydrogels**} & \multicolumn{4}{c}{**Coordinates**} \\ \hline  & **T \({}^{\ast}\) (\({}^{\circ}\)C)** & **L\({}^{\ast}\)** & **a\({}^{\ast}\)** & **b\({}^{\ast}\)** & \(\Delta\)E \\ \hline  & 140 & \(25.14\pm 0.14\)\({}^{\text{a}}\) & \(0.53\pm 0.06\)\({}^{\text{f}}\) & \(1.30\pm 0.07\)\({}^{\text{d}}\) & - \\  & 160 & \(24.24\pm 1.00\)\({}^{\text{a}}\) & \(-0.46\pm 0.13\)\({}^{\text{h}}\) & \(2.43\pm 0.23\)\({}^{\text{c}}\) & \(1.74\pm 0.88\) \\
**Bark** & 180 & \(25.64\pm 0.84\)\({}^{\text{a}}\) & \(0.002\pm 0.09\)\({}^{\text{g}}\) & \(0.35\pm 0.12\)\({}^{\text{e}}\) & \(1.20\pm 0.70\) \\  & 200 & \(25.20\pm 0.69\)\({}^{\text{a}}\) & \(0.47\pm 0.07\)\({}^{\text{f}}\) & \(0.45\pm 0.07\)\({}^{\text{e}}\) & \(0.86\pm 0.55\) \\  & 220 & \(25.09\pm 0.21\)\({}^{\text{a}}\) & \(3.86\pm 0.13\)\({}^{\text{c}}\) & \(1.45\pm 0.13\)\({}^{\text{d}}\) & \(3.33\pm 0.12\) \\  & 240 & \(24.81\pm 0.58\)\({}^{\text{a}}\) & \(6.93\pm 0.45\)\({}^{\text{a}}\) & \(3.74\pm 0.05\)\({}^{\text{b}}\) & \(6.85\pm 0.59\) \\  & 140 & \(20.02\pm 0.86\)\({}^{\text{c}}\) & \(-0.42\pm 0.24\)\({}^{\text{h}}\) & \(2.64\pm 0.13\)\({}^{\text{c}}\) & - \\  & 160 & \(24.65\pm 0.66\)\({}^{\text{a}}\) & \(-0.34\pm 0.04\)\({}^{\text{h}}\) & \(0.29\pm 0.08\)\({}^{\text{f}}\) & \(5.20\pm 0.28\) \\
**Leaves** & 180 & \(24.49\pm 0.43\)\({}^{\text{a}}\) & \(-0.52\pm 0.07\)\({}^{\text{h}}\) & \(-0.13\pm 0.06\)\({}^{\text{g}}\) & \(5.26\pm 0.46\) \\  & 200 & \(23.52\pm 0.80\)\({}^{\text{b}}\) & \(-0.38\pm 0.09\)\({}^{\text{h}}\) & \(3.78\pm 0.16\)\({}^{\text{b}}\) & \(3.68\pm 0.48\) \\  & 220 & \(22.85\pm 0.39\)\({}^{\text{b}}\) & \(-0.05\pm 0.18\)\({}^{\text{g}}\) & \(4.37\pm 0.07\)\({}^{\text{a}}\) & \(3.34\pm 0.48\) \\  & 240 & \(23.28\pm 1.65\)\({}^{\text{b}}\) & \(5.37\pm 0.75\)\({}^{\text{b}}\) & \(4.43\pm 0.56\)\({}^{\text{a}}\) & \(6.88\pm 1.04\) \\  & 140 & \(24.96\pm 0.16\)\({}^{\text{a}}\) & \(2.94\pm 0.06\)\({}^{\text{d}}\) & \(2.29\pm 0.30\)\({}^{\text{c}}\) & - \\  & 160 & \(23.96\pm 0.80\)\({}^{\text{a,b}}\) & \(1.81\pm 0.11\)\({}^{\text{e}}\) & \(1.27\pm 0.28\)\({}^{\text{d}}\) & \(1.82\pm 0.69\) \\
**Petioles** & 180 & \(25.11\pm 0.90\)\({}^{\text{a}}\) & \(-0.45\pm 0.09\)\({}^{\text{h}}\) & \(0.20\pm 0.03\)\({}^{\text{f}}\) & \(3.98\pm 0.74\) \\  & 200 & \(23.98\pm 0.80\)\({}^{\text{a,b}}\) & \(-0.54\pm 0.07\)\({}^{\text{h}}\) & \(-0.02\pm 0.06\)\({}^{\text{g}}\) & \(4.29\pm 0.64\) \\  & 220 & \(25.03\pm 0.43\)\({}^{\text{a}}\) & \(-0.62\pm 0.03\)\({}^{\text{h}}\) & \(0.41\pm 0.04\)\({}^{\text{e}}\) & \(4.02\pm 0.27\) \\  & 240 & \(25.11\pm 0.33\)\({}^{\text{a}}\) & \(2.85\pm 0.05\)\({}^{\text{d}}\) & \(1.52\pm 0.14\)\({}^{\text{d}}\) & \(0.79\pm 0.21\) \\ \hline \hline \end{tabular}  
* Data values are given as average values \(\pm\) standard deviations. Data in a column with different superscript letters are significantly different at the \(p\leq 0.05\) level. Statistical analysis was separately made for starch- and gelatin-based hydrogels. Note here that for \(\Delta\)E determination, 140 \({}^{\circ}\)C was selected as the reference temperature.  
\end{table} 
Table 2: _Cont._Figure 3 shows the influence of representative Paulownia extracts on the mechanical spectra of gelatin-based hydrogels. Again, the monitoring of both elastic and viscous moduli with frequency allowed identifying characteristic gel profiles (G' > G'', and almost frequency independent). Similar viscoelastic behavior was observed when compared with their counterparts made with starch, although lower values (around 10 times) of both moduli were identified. Within the gelatin-based hydrogels, the strongest gelling features were found for those formulated with petioles followed by hydrogels in the presence of banks and leaves, as above for starch-based hydrogels. In this case, the presence of Paulownia extracts on the gelatin-based hydrogels involved a softening (around five times) regarding the pure matrix, which suggest to be linked with the water holding capacity.