# Hake Fish Preservation Using Plant-Based Impregnated Polylactic Acid Food Films as Active Packaging
## 3 Results and Discussion
### Preservation of Hake Fillets
#### 3.2.2 Effects of Storage on the Physical and Chemical Properties
Analyzing the evolution of each part individually, the \(L^{*}\) values of the flesh tended to have lower values along storage, both when using the control and the impregnated films with respect to the initial sample, with statistical differences from day 5. Samples packaged into impregnated films showed more differences to the initial day than those packaged under the control film. Regarding the \(a^{*}\) parameter, the values decreased along storage in all samples, showing differences among the treatments from day 9. Therefore, the influence of the chlorophylls was not as determinant on the color variation as the evolution of the fish itself. In this sense, despite the high green color of the impregnated films, the fish did not show a green tonality. On the other hand, the color difference of the fillets was mostly due to the significant increase in the \(b^{*}\) values when packaged using the impregnated films. This denotes an increase in the yellow hue promoted by the presence of the extract. When analyzing the skin, in general, the color variations of both the light and dark parts were mostly influenced by the storage time rather than the film treatment in all parameters, showing the same trends as those previously mentioned on the flesh. The most evident differences in the treatments were due to the \(b^{*}\) values, where these values were statistically higher in the impregnated films from day 7 in the case of the dark skin, and from day 2 in the light skin, tending to yellow hues. In a comparison with the initial sample, the differences were related to the higher spoilage of the fillets (Section 3.2.3) in the control film, and to the possible cessation of the compound when the impregnated film was used. In all samples, differences were observed with respect to day 0, which shows the fast spoilage of the fish. In general terms, fish packaged with the impregnated film showed higher \(\Delta\)E values, mainly due to a higher \(b^{*}\) contribution (yellow hue). However, it must be noted that the differences in \(\Delta\)E values among the impregnated and control films were generally less than 3 in most cases (Figure 3, lowercase letters). This denotes only slight variations that are imperceptible to the naked eye, as can also be observed in Figure 2.  
Figure 4 shows the effect of the storage time on the drip loss, water activity and pH values of the hake fillets packaged in the impregnated and non-impregnated films (control). The maintenance of moisture in fresh-cut products with a high \(\mathrm{a_{w}}\) is a key point in the polymer formulation. It should prolong the humidity as much as possible, avoiding condensation inside the package, to prevent the proliferation of microorganisms. [PERSON] et al. [55] pointed out that PLA material has a relatively high water vapor permeability coefficient. As a result, when kept refrigerated, the raw material can gradually lose moisture. This phenomenon was reflected in both the \(\mathrm{a_{w}}\) reduction and the drip loss observed in both cases, and in the samples packaged in impregnated PLA to a lesser extent [55]. As can be seen in Figure 4a, the behavior in this study was similar. Drip loss showed an increasing tendency in both cases, being higher in the control film (24.69 \(\pm\) 2.59%) compared to the impregnated one (18.17 \(\pm\) 1.48%) at the end of the experiment. This drip loss was clearly reflected in the \(\mathrm{a_{w}}\), whose values decreased for both types of samples. This decrease was more pronounced in the non-impregnated samples at the end of the storage time (Figure 4b). Therefore, impregnation appears to have preserved the moisture of the samples over long storage periods. In the study carried out by [PERSON] et al. [54], it was observed that the coating of bound shark (_Mustelus mustelus_) fillets with edible gelatin enriched with _Moringa oleifera_ extract reduced syneresis and decreased the weight loss by 26% over the control (fillets without coating). They also reported higher values than those observed in this work for impregnated film.