Chitosan-gelatin composites and bi-layer films with potential antimicrobial activity

The aims of this work were to develop composite (Chi-Ge) and bi-layer (Chi/Ge) edible and biodegradable films based on gelatin and chitosan. physico-chemical properties such as water resistance, transparency and color were analyzed. Composite and bi-layer systems were uniform, homogeneous and thin; they showed a compact structure indicating a good compatibility between components, which could interact by strong hydrogen bonding, as was confirmed by FTIR. Water vapor permeability (WVP) was determined. Both, bi-layer and laminated systems resulted effective alternatives to reduce WVP of chitosan control film. The tensile strength of composite and bi-layer system did not differ significantly (P > 0.05), but elongation at break of composite films was 40% higher (P < 0.05) than that of bi-layer film. Antimicrobial activity of the films was analyzed. The results indicated that both E. coli and L. monocytogenes showed sensitivity to all the films forming solutions. The inhibition halos of both pathogens to the solutions of Chi and Chi-Ge showed to be extremely sensitive. Results obtained with edible films indicated that only E. coli was sensitive to the combination Chi-Ge and Chi/Ge. Neat Chi film did not induce significant inhibition halos for none of the pathogens, which was quite surprising and still under study.