Physical and antioxidant properties of chitosan and methylcellulose based films containing resveratrol

New trends in edible films focus on the improvement of their functionality through the incorporation of active compounds, such as antimicrobial or antioxidant agents. Resveratrol is a natural antioxidant found in a variety of plant species, such as grapes, and could be used for minimizing or preventing lipid oxidation in food products, retarding the formation of oxidation products, maintaining nutritional quality and prolonging the food shelf life. The aim of this work was to develop and characterize two different polymeric composite films (made with chitosan (CH) and methylcellulose (MC)) containing different amounts of resveratrol. This compound could be incorporated efficiently into both films, but provoke structural changes in the matrices, which became less stretchable (65–70% reduction of deformation at break at the greatest resveratrol content) and resistant to fracture (26 and 54% reduction of tensile at break for MC and CH, respectively, at the greatest resveratrol content) more opaque (significant reduction of the internal transmittance) and less glossy (about 60–65% reduction of gloss at the greatest resveratrol content). Film barrier properties were hardly improved by the presence of resveratrol; water vapour and oxygen permeability tend to slightly decrease when resveratrol was incorporated into both polymers. Composite films showed antioxidant activity, which was proportional to the resveratrol concentration in the film. None of the films showed antimicrobial activity against Penicillium italicum and Botrytis cinerea. Thus, these films could be applied to food products which are sensitive to oxidative processes to prolong their shelf life.

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► Resveratrol was efficiently incorporated into both chitosan and methylcellulose films.
► Composite films exhibited antioxidant properties but no antifungal activity against P. italicum and B. cinerea.
► Barrier properties, films' mechanical resistance, gloss and transparency decreased in composite films.
► Resveratrol incorporation induced changes in the semi-crystalline arrangement of CH and MC.