## 3 Results
### Antioxidant Activity  
Finally, the antioxidant capacity of the GA released from the PLA films was evaluated by the DPPH radical scavenging assay to assess their potential in bioactive packaging applications. DPPH is a stable radical with a maximum absorption at 517 nm that can readily undergo scavenging by an antioxidant such as polyphenols [47]. This method is based on the reduction of the relatively stable radical, that is, DPPH, to the formation of a non-radical form in the presence of hydrogen donating antioxidants. GA is a phenolic compound containing hydroxyl groups attached to the benzene ring in the ortho position so that it possesses electron and/or hydrogen donor ability [48]. Indeed, the antioxidant activity of these compounds is mainly due to their redox properties, which allows them to act as reducing agents, hydrogen donators, and singlet oxygen quenchers having metal-chelating capacities [49]. Table 4 shows the antioxidant capacity of the GA released from the bi- and multilayer PLA films after their immersion for two, six, and ten weeks in the saline medium. As one can observe in the table above, the GA released from all the PLA films showed antioxidant activity confirming that electrospinning process was successful in retaining the bioactivity of GA [14; 50], even after the electrospun mats had been subjected to a high electrical potential during the fiber producing process as well as the thermal post-treatment. The antioxidant activity of the GA released from the PLA films was in agreement with the total amounts of the as-released GA, previously shown in Figure 5a. Therefore, in the case of the bilayer PLA films, a strong antioxidant activity was attained after two weeks of immersion in the medium while it progressively decreased over time. On the contrary, the multilayer PLA films provided a release of GA that showed a relatively low DPPH inhibition in first weeks. However, after ten weeks, the PLA films containing the electrospun GA-loaded interlayer achieved a stronger DPPH inhibition, indicating that it effectively protects the polyphenol over longer periods. Based on the present observations, it can be considered that the GA release and, thus, the GA antioxidant functionality can be controlled by the appropriate design of PLA films containing electrospun coating and interlayers. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Film**} & \multicolumn{3}{c}{**Inhibition (\%)**} \\ \cline{2-4}  & **2 Weeks** & **6 Weeks** & **10 Weeks** \\ \hline Bilayer 1h & 42.4 \(\pm\) 0.7 1  & 38.4 \(\pm\) 0.9 2  & 25.6 \(\pm\) 1.2 3  \\ Bilayer 2h & 65.7 \(\pm\) 0.9 1  & 54.9 \(\pm\) 1.2 1  & 47.7 \(\pm\) 0.9 2  \\ Bilayer 3h & 96.0 \(\pm\) 2.4 1  & 78.9 \(\pm\) 1.3 1  & 54.7 \(\pm\) 1.3 1  \\ Multilayer 1h & 5.9 \(\pm\) 0.8 2  & 29.2 \(\pm\) 0.7 2  & 38.1 \(\pm\) 0.7 2  \\ Multilayer 2h & 8.1 \(\pm\) 0.8 2  & 37.4 \(\pm\) 1.0 2  & 52.4 \(\pm\) 1.2 2  \\ Multilayer 3h & 12.3 \(\pm\) 1.2 2  & 48.7 \(\pm\) 0.9 2  & 71.4 \(\pm\) 0.8 2  \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Inhibition (%) of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) of the gallic acid (GA) released from the polylactide (PLA) films. In this sense, other previous studies have shown the potential of electrospinningning to encapsulate GA in order to retain its antioxidant activity for active packaging applications. In the study performed by [PERSON] et al. [14], GA was successfully encapsulated at 5-20 wt% in zein nanofibers by electrospinningning. It was found that the DPPH scavenging abilities of the GA-loaded zein electrospun fibres varied from 58% to 89%, showing that there was no significant difference for DPPH scavenging activity of GA before and after the electrospinningning process. Similar antioxidant properties have been recently observed by [PERSON] et al. [27], who loaded GA at 2-10 wt% into electrospun hydroxypropyl methylcellulose (HPMC)/ polyethylene oxide (PEO) blend nanofibers.