Development and characterization of grey triggerfish gelatin/agar bilayer and blend films containing vine leaves bioactive compounds

The present study aims to develop natural biopolymer bioactive edible films. Particularly, blend (F-Bl) and bilayer (F-Bi) films based on grey triggerfish skin gelatin (G) and agar (A), incorporated or not with vine leaves ethanolic extract (VLE), at 5 and 10 mg/mL, were prepared using the casting method. First, VLE presented an important antioxidant potential evaluated by the iron (Fe2+) chelating activity, ferric (Fe3+) reducing antioxidant power, beta-carotene bleaching protection and DPPH center dot-radical scavenging activity. Furthermore, VLE presented interesting antibacterial and antifungal activities. On the other hand, the composite films were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), physicochemical, and thermal analyses. SEM micrographs showed that agar and gelatin were compatible. Moreover, the mechanical properties results showed that F-Bl and F-Bi were mechanically stronger and more deformable than control films. This change in mechanical properties can be explained by the formation of a dense network after agar addition, due to the interactions with the gelatin matrix. After their incorporation into polymer network, VLE increased slightly the thermal stability, while it improved greatly the antioxidant activity of the composite films (gelatin and agar) in a dose dependent manner. Thus, results encourage the further use of gelatin/agar/VLE films as active food packaging material.