## 3 Results and Discussion  
### Characterization of Films Processed at Laboratory Scale  
LDPE and LDPE_CAR monolayer films were processed at laboratory scale to evaluate the viability of \(\beta\)-carotene incorporation in a LDPE matrix. Firstly, colour characteristics of the films were determined. Table 1 shows that \(a^{*}\) and \(b^{*}\) values were higher in LDPE_CAR than in LDPE confirming that the active compound incorporation causes, as it is described elsewhere [21; 27], an intense yellow-orange colour. In addition, a decrease of around 25% in the value of \(L^{*}\) parameter was observed when \(\beta\)-carotene was present in the LDPE_CAR formulation, indicating an increase in the opacity of the films in comparison with the control one. These results are in line with those obtained in other studies carried out by [PERSON] et al. [28], in which a significant decrease in \(L^{*}\) value was identified as a consequence of the incorporation of hydroxytyrosol as antioxidant compound in polycaprolactone films. In relation to the thermal properties of the films, the shape of the DSC melting curve depends on the thermal history of the sample, thus a peak is observed at 108 \({}^{\circ}\)C related to the melting of LDPE in LDPE and LDPE_CAR samples, as it was reported in previous studies [19; 29]. In relation to the crystallization process, values of T\({}_{\text{c}}\) around 97 \({}^{\circ}\)C are obtained in both materials and significant differences were observed in the melting and crystallization enthalpies. Regarding the TGA results, the initial degradation temperatures (T\({}_{\text{ini}}\)), determined at 5% weight loss, and maximum degradation temperatures (T\({}_{\text{max}}\)) obtained for all formulations are shown in Table 2. The incorporation of \(\beta\)-carotene to the formulation brings about a significant effect on the thermal stability of the obtained active films (\(p<0.05\)). In this sense, the addition of a theoretical amount of 10 wt.% \(\beta\)-carotene to LDPE films resulted in an increase in the T\({}_{\rm max}\) of 3%. Finally, oxygen absorption capacity of LDPE_CAR film was evaluated. As can be seen in Figure 2, LDPE_CAR film was able to absorb 1.39 \(\pm\) 0.10 mL O\({}_{2}\) per g of film. An increase in the absorbed oxygen was observed as the amount of film increase from 0.5 to 1.5 g confirming a linear behaviour when the absorbed oxygen (mL) was represented versus the film mass (g). No previous studies have been found related to the incorporation of \(\beta\)-carotene to LDPE films with the purpose to act as an oxygen scavenger, without the need of any additional activation process. All the obtained results confirmed that \(\beta\)-carotene incorporation in LDPE matrices at laboratory scale produces valuable films in terms of thermal properties and oxygen absorption capacity. \begin{table}
\begin{tabular}{c c c c c} \hline  & \(\mathbf{L^{*}}\) & \(\mathbf{a^{*}}\) & \(\mathbf{b^{*}}\) & \(\mathbf{\Delta E}\) \\ \hline LDPE & 99.0 \(\pm\) 0.3 \({}^{\rm a}\) & 0.03 \(\pm\) 0.03 \({}^{\rm b}\) & 0.1 \(\pm\) 0.04 \({}^{\rm c}\) & 0.27 \(\pm\) 0.06 \({}^{\rm c}\) \\ ML & 99.6 \(\pm\) 0.2 \({}^{\rm a}\) & 0.01 \(\pm\) 0.01 \({}^{\rm b}\) & 0.25 \(\pm\) 0.05 \({}^{\rm c}\) & 0.24 \(\pm\) 0.09 \({}^{\rm c}\) \\ LDPE\_CAR & 75.2 \(\pm\) 0.4 \({}^{\rm c}\) & 15.2 \(\pm\) 0.6 \({}^{\rm a}\) & 77.4 \(\pm\) 0.6 \({}^{\rm a}\) & 82.1 \(\pm\) 0.4 \({}^{\rm a}\) \\ ML/LDPE\_CAR & 98.15 \(\pm\) 0.1 \({}^{\rm b}\) & \(-\)3.73 \(\pm\) 0.09 \({}^{\rm c}\) & 9.7 \(\pm\) 0.4 \({}^{\rm b}\) & 10.4 \(\pm\) 0.4 \({}^{\rm b}\) \\ \hline \end{tabular} \({}^{\#}\) Results expressed as the mean \(\pm\) standard deviation of three replicates (\(\alpha\) = 0.05). \({}^{\dagger}\) Different superscripts in the same column indicate statistically significant different values (\(p<0.05\)).  
\end{table} 
Table 1: Colour parameters (\(L^{*}\), \(a^{*}\), \(b^{*}\), and \(\Delta E\)) of monolayer and multilayer studied films \({}^{\#,\dagger}\).