## 3 Results and Discussion
### Films Characterization
#### 3.1.7 Antioxidant Activity  
Antioxidant packaging is a very promising alternative for extending food products shelf-life. Enriching films with antioxidants allows nutritional and esthetic quality aspects to be enhanced without affecting the integrity of the food product. The DPPH radical assay has been widely used to test the ability of compounds as free radical scavengers or hydrogen donors in order to evaluate antioxidant activity [53]. Neat PCL film did not show any radical scavenging activity, as expected. On the other hand, films containing 3 and 6 wt.% of ASE presented RSA values of \(16\pm 1\%\) and of \(20\pm 1\%\), respectively. No RSA was obtained in any formulation after a second sequential extraction which was related to an efficiently release of the majority of antioxidant compounds from the polymer matrix to the solvent during the first extraction step. As a result, the incorporation of ASE conferred some antioxidant power to PCL/ASE films compared to neat PCL which was attributed to the presence of phenolic compounds in ASE as it has been previously reported in the literature [28]. The free-radical scavenging ability of phenolics is mainly due to their redox properties, which allow them to act as reducing agents, hydrogen donators and singlet oxygen quenchers [53]. Then, the free radical scavenging of ASE could be attributed to the presence of phenolic compounds that can migrate through the polymer matrix to the food product. The obtained results are in accordance with those obtained by [PERSON] et al. [15] reporting RSA values around 20% at short initial migration times for PCL-based films added with \(\alpha\)-tocopherol by following the DPPH method. Similar results were found for gelatin-based films additivated with curcumin ethanol extract [48], electrospun PCL films with sage natural extract [51], acetylated hemicellulose-nanocellulose-PCL films with mango peel polyphenols [55] and chitosan films containing tea extracts [53], being the obtained RSA values dependent on the type and concentration of the active additive used in the formulations.  
The effect of manufacturing conditions is also an important issue to be considered and processing temperatures could play a major role in determining the efficiency of the obtained active films [45; 61]. According to DPPH and TGA results, it was concluded that ASE was thermally stable during the whole processing window of PCL/ASE films [59].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Thermal property** & **Neat PCL** & **PCL3** & **PCL6** \\ \hline \(\Delta\)H\({}_{\text{c}}\) (\(\text{$\text{J}$}\) g\({}^{-1}\)) & \(59\pm 1\)\({}^{\text{a}}\) & \(62\pm 4\)\({}^{\text{a}}\) & \(59\pm 1\)\({}^{\text{a}}\) \\ T\({}_{\text{c}}\) (\({}^{\circ}\)C) & \(30\pm 1\)\({}^{\text{a}}\) & \(29\pm 1\)\({}^{\text{a}}\) & \(29\pm 1\)\({}^{\text{a}}\) \\ \(\Delta\)H\({}_{\text{m}}\) (\(\text{$\text{J}$}\) g\({}^{-1}\)) & \(59\pm 1\)\({}^{\text{a}}\) & \(58\pm 3\)\({}^{\text{a}}\) & \(57\pm 2\)\({}^{\text{a}}\) \\ T\({}_{\text{m}}\) (\({}^{\circ}\)C) & \(55\pm 1\)\({}^{\text{a}}\) & \(54\pm 1\)\({}^{\text{a}}\) & \(54\pm 2\)\({}^{\text{a}}\) \\ T\({}_{\text{g}}\) (\({}^{\circ}\)C) & \(-61\pm 2\)\({}^{\text{a}}\) & \(-63\pm 2\)\({}^{\text{a}}\) & \(-64\pm 1\)\({}^{\text{a}}\) \\ T\({}_{\text{ini}}\) (\({}^{\circ}\)C) & \(385\pm 2\)\({}^{\text{a}}\) & \(383\pm 3\)\({}^{\text{a}}\) & \(382\pm 3\)\({}^{\text{a}}\) \\ T\({}_{\text{max}}\) (\({}^{\circ}\)C) & \(415\pm 1\)\({}^{\text{a}}\) & \(415\pm 1\)\({}^{\text{a}}\) & \(415\pm 1\)\({}^{\text{a}}\) \\ \hline \hline \end{tabular} Thermal properties (mean \(\pm\) SD; \(n=3\)) of neat PCL and PCL/ASE composite films. Different superscripts within the same row indicate statistically significant different values (\(p<0.05\)).  
\end{table}
Table 2: Thermal properties of neat PCL and PCL/ASE composite films obtained by DSC and TGA.