## 3 Results and Discussion
### Films Characterization
#### 3.1.3 Barrier Properties  
Barrier properties of packaging materials to moisture and oxygen are directly related to their final application and they could affect the food product quality and shelf-life. Water vapour and oxygen are two of the main permeants studied in food packaging applications, as they may transfer from the internal or external environment through the polymer packaging wall, resulting in a continuous change in product quality and shelf-life [52]. The results obtained for OTR, WVP and water absorption properties of the studied films are shown in Table 1. As it can be seen, the addition of ASE to PCL did not significantly affect the OTR values of the obtained films (\(p>0.05\)). However, some increase (\(p<0.05\)) in WVP and water absorption (after 120 h of immersion) was observed for PCL/ASE films compared to neat PCL. As a result, neat PCL showed a higher hydrophobic behaviour compared to the active films with ASE. Significant decreases in water barrier properties have been reported with the addition of plant extracts to different biopolymer films. [PERSON] and [PERSON] [46] found an increase in WVP values with the addition of grapefruit seed extract in agar-based films which was related to a reduction in intermolecular interactions between the components and the changing pore size of the films. [PERSON] et al. [51] reported changes in water permeability induced by the addition of sage extract into PCL due to the higher affinity for water of the natural extract in contrast to PCL. The polyphenolic composition of ASE may determine the final barrier properties of the developed films. In a previous study [28], it was found that ASE extracted from Guara almond cultivar showed high total flavonoids content (1162 ug g\({}^{-1}\) almond skin) and total phenolic content (119 mg of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Property** & **Neat PCL** & **PCL3** & **PCL6** \\ \hline \(L^{*}\) & \(78.0\pm 1.2\) a  & \(72.4\pm 0.3\) b  & \(61.9\pm 0.4\) c  \\ \(a^{*}\) & \(-0.7\pm 0.4\) a  & \(3.4\pm 0.2\) b  & \(8.5\pm 0.1\) c  \\ \(b^{*}\) & \(-1.1\pm 0.2\) a  & \(15.9\pm 0.4\) b  & \(21.2\pm 0.4\) c  \\ \(\Delta E^{*}\) & - & \(18.3\pm 0.6\) a  & \(29.0\pm 0.6\) b  \\ \hline Water absorption (\%, 120 h) & \(0.38\pm 0.09\) a  & \(1.05\pm 0.05\) b  & \(0.98\pm 0.21\) b  \\ OTR (cm\({}^{3}\) mm m\({}^{-2}\) day) & \(95\pm 8\) a  & \(109\pm 5\) a  & \(115\pm 8\) a  \\ WVP \(\times 10^{-4}\) (kg m Pa\({}^{-1}\) s\({}^{-1}\) m\({}^{-2}\)) & \(1.8\pm 0.1\) a  & \(2.4\pm 0.3\) b  & \(2.5\pm 0.4\) b  \\ \hline Young’s modulus (MPa) & \(352\pm 20\) a  & \(336\pm 20\) a  & \(340\pm 15\) a  \\ Elongation at break (\%) & \(77\pm 12\) a  & \(79\pm 14\) a  & \(74\pm 10\) a  \\ Tensile strength (MPa) & \(16\pm 1\) a  & \(13\pm 2\) a  & \(14\pm 3\) a  \\ \hline \hline \end{tabular} Colour parameters (\(L^{*}\), \(a^{*}\), \(b^{*}\), \(\Delta E^{*}\); mean \(\pm\) SD; \(n=5\)), barrier (mean \(\pm\) SD; \(n=3\)) and mechanical properties (mean \(\pm\) SD; \(n=5\)) 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 1: The results obtained for colour, barrier and mechanical properties of the studied films. Figure 2: Visual appearance of neat PCL (**A**), PCL3 (**B**) and PCL6 (**C**) films. quercetin equivalent g-1 almond skin), with the isorhannetin-3-O-rutinoside content being noticeably followed by kaempfer-3-O-rutinoside, quercetin-3-O- rutinoside, naringenin-7-O-glucoside, isorhannetin-3-O-glucose, (\(-\))-epicatechin, (\(+\))-catechin and, finally, naringenin contents (Figure S1). Thus, the hydrophilic nature of polyphenols present in ASE may induce an increase in the affinity of active films for water [51; 53] by unveiling the availability of hydroxyl groups to bind water molecules [45; 54].