Crosslinking agents effect on gelatins from carp and tilapia skins and in their biopolymeric films

The extracted gelatins from carp and tilapia skins were chemically crosslinked by electrolytes (NaCl and MgSO4) and nonelectrolytes (gallic acid and citric acid) agents and, the fish gelatins films were produced by casting. Rheological, chemical and physicochemical properties were evaluated. All crosslinked films showed a significant increase in tensile strength and a slight reduction in elongation compared to non–crosslinked films. The crosslinked films with nonelectrolytes presented the highest reductions in water vapor permeability. Fourier Transform Infrared spectra, X–Ray Diffraction and Scanning Electron Microscopy showed the interactions between protein/agents and the changes in amorphous structure of the films, which presented surfaces in chains of twisted shape. Differential Scanning Calorimetry demonstrated that the incorporations of gallic acid and citric acid improved the films thermal stability. The results showed that the chemical crosslinking can be used to improve the quality of fish skin gelatin films and, thus, these films can be an alternative to food packaging, as well to improve added value of the fish waste.