Filmes de gelatina e galactomanana incorporados com nanocelulose de fibra de algaroba (Prosopis juliflora)

Abstract

This work seeks developing biodegradable films from gelatin obtained from waste tilapia (Oreochromis niloticus) and galactomannan extracted from Mesquite (Prosopis juliflora). An experimental design type simplex centroid was used to assess the effect of the ratios between the two components - gelatin (GE) and galactomannan (GA) – on the properties of the formed films. The results of the films obtained from the mixture design indicated that the film containing a GE:GA of 1:1 showed the best results for water vapor permeability and mechanical tests, being this film later submitted to the incorporation of cellulose nanocrystals extracted from the leguminous of the mesquite. The formulation of the films of gelatin and galactomannan was performed using glycerol 25% (on a dry basis of gelatin and galactomannan) varying the amount of nanocellulose from mesquite fiber on concentrations of 2.5, 5 and 7, 5% (dry basis of gelatin and galactomannan). The films were obtained by casting and were characterized in terms of their water vapor permeability (WVP), mechanical properties (tensile strength, elongation and elastic modulus), optical scanning electron microscopy (SEM), optical microscopy (OM), Fourier Transform Infrared (FTIR), opacity, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The nanocellulose at 5% was effective to reduce the WVP. Nanocellulose increased the tensile strength and modulus with a slight decrease at the highest concentration (7.5 %). Nanocellulose did not affect significantly the film elongation. TGA analysis showed that increasing nanocellulose concentrations increased the film thermal stability, and the DSC analysis proved the formation of blends. The microscopy images revealed the formation of clusters of nanocrystals as their concentration increased. FTIR analysis revealed no major changes in the film structure apart from offset or reduction of some bands. The opacity increased with the incorporation of nanocellulose, although it did not increase with increasing nanocellulose concentrations.