## 3 Results
### Optical Properties: Color and Transparency  
Film color and transparency are not only important factors in food packaging designs, but also very useful for evaluating the filler-polymer matrix compatibility. Table 2 summarizes the color coordinates in terms of \(L^{*}\), \(C_{ab}\)*, and \(h_{ab}\)* as well as the total color difference (\(\Delta E^{*}\)) with respect to the neat TPS films without DH treatment and CMFs and the opacity coefficient of the different films. Likewise, the \(T_{i}\) spectra of the different films are shown in Figure 5. Both the CMF incorporation and starch DH modification significantly (\(p<0.05\)) affected the evaluated optical properties. Comparison of TPS and TPSDH films without fibers permits to elucidate that DH gave rise to slightly darker films with more saturated, that is, higher C\({}_{ab}\)* values, and a yellower color, which suggest that Maillard or sugar caramelization reactions could occur during thermal treatment of native starch. Likewise, as the CMF concentration increased, both TPS and TPSDH films exhibited a slight decrease in their lightness (\(L^{*}\)) while color saturation (\(C_{ab}\)*) increased and hue tended to be more yellowish. This was reflected on the \(\Delta E^{*}\) values, in which the color coordinates \(L^{*}\), \(a^{*}\), and \(b^{*}\) of the TPS control film were used as a reference. In the TPS films without DH treatment, the \(\Delta E^{*}\) values attained after the incorporation of low contents of CMFs were below 1 indicating unnoticeable color changes, whereas only in the microcomposite with 5 wt% CMFs, that is, TPS5, an unexperienced observer can already observe color differences (\(2\leq\Delta E^{*}\leq 3.5\)). In the TPSDH films, as opposite, the combined effect of dispersed phases, that is, CMFs and non-gelatinized starch granules, and colored compounds formed during thermal modification of starch [31; 54], gave rise to higher color variations with respect to the neat TPS films. Thus, the TPSDH and its microcomposite with the lowest CMF content showed clear noticeable differences (\(3.5\leq\Delta E^{*}\leq 5\)), whereas the samples with higher fiber contents yielded films with a noticeable different color (\(\Delta E^{*}\geq 5\)). \begin{table}
\begin{tabular}{c c c c c c} \hline
**Formulation** & \(L^{*}\) & \(C_{ab}\)* & \(h_{ab}\)* & \(\Delta E\)* & **O** \\ \hline TPS & \(88.5\pm 0.1\) *\({}^{1.1}\) & \(7.6\pm 0.1\) *\({}^{2}\) & 92.6 \(\pm\) 0.1 *\({}^{1.1}\) & - & \(0.141\pm 0.001\)*\({}^{2.2}\) \\ TPS1 & \(88.5\pm 0.1\)*\({}^{3.3}\) & \(7.5\pm 0.2\)*\({}^{2}\) & 92.8 \(\pm\) 0.1 *\({}^{1.1}\) & 0.07 \(\pm\) 0.01 * \({}^{0.16}\) \(\pm\) 0.009 *\({}^{0.2}\) \\ TPS3 & \(88.1\pm 0.2\)*\({}^{5.5}\) & \(8.2\pm 0.3\)*\({}^{2.2}\) & 92.6 \(\pm\) 0.2 *\({}^{1.1}\) & 0.70 \(\pm\) 0.02 * \({}^{0.15}\) \(\pm\) 0.005 *\({}^{0.2}\) \\ TPS5 & \(87.6\pm 0.2\)*\({}^{7.7}\) & \(9.4\pm 0.3\)*\({}^{2.2}\) & 91.5 \(\pm\) 0.2 *\({}^{1.1}\) & 2.03 \(\pm\) 0.01 *\({}^{0.14}\) \(\pm\) 0.005 *\({}^{0.2}\) \\ TPSDH & \(86.0\pm 0.1\)*\({}^{2.2}\) & \(11.9\pm 0.5\)*\({}^{1.1}\) & 89.2 \(\pm\) 0.2 *\({}^{0.22}\) & 4.76 \(\pm\) 0.05 *\({}^{0.16}\) \(\pm\) 0.001 *\({}^{0.1}\) \\ TPSDH1 & \(86.2\pm 0.2\)*\({}^{4.4}\) & \(11.3\pm 0.2\)*\({}^{1.1}\) & 89.5 \(\pm\) 0.3*\({}^{0.2}\) & 4.64 \(\pm\) 0.10*\({}^{0.1}\) & 0.163 \(\pm\) 0.006 *\({}^{0.1}\) \\ TPSDH3 & \(85.4\pm 0.1\)*\({}^{6.6}\) & \(12.4\pm 0.2\)*\({}^{1.1}\) & 88.9 \(\pm\) 0.1 *\({}^{0.2}\) & 6.24 \(\pm\) 0.01*\({}^{0}\) & 0.171 \(\pm\) 0.007 *\({}^{0.1}\) \\ TPSDH5 & \(84.5\pm 0.1\)*\({}^{6.8}\) & \(14.2\pm 0.2\)*\({}^{1.1}\) & 88.8 \(\pm\) 01 *\({}^{0.2}\) & 7.88 \(\pm\) 0.15*\({}^{0}\) & 0.156 \(\pm\) 0.007 *\({}^{0.1}\) \\ \hline \end{tabular}  
* Different subscript letters indicate significant differences between samples of the same group (TPS or TPSDH films). Different numbers indicated significant differences between TPS and TPSDH samples with the same ratio of CMF (Tukey test, \(p<0.05\)).  
\end{table}