Impact of functional properties and release kinetics on antioxidant activity of biopolymer active films and coatings

•Active chitosan-fish gelatin film containing natural antioxidants.•Improvement of films mechanical and barrier properties after antioxidants addition.•Charge-charge interactions with the ammonium groups of gelatin and/or chitosan for phenolic acids.•The effective diffusion coefficient of tyrosol was 170 times greater than phenolic acids.•Antioxidant activity can be limited/influenced by the release kinetic.

This work deals with the study of the release kinetics of some natural antioxidants (ferulic acid, caffeic acid and tyrosol) from chitosan-fish gelatin edible films immersed ethanol at 96%, as well as the kinetics of their antioxidant activity using the DPPH assay. The aim was to determine how film functional properties influence the release kinetic and antioxidant activity. The addition of antioxidants to chitosan-fish gelatin matrix decreased the water vapour permeability by more than 30%. The tensile strength (TS) increased up to 50% after the incorporation of antioxidants. Some molecular interactions between polymer chains and antioxidants were confirmed by FTIR where spectra displayed a shift of the amide-III peak. Films containing caffeic acid or a caffeic-ferulic acid mixture exhibited the highest radical scavenging activity, leading to a 90% antioxidant activity at equilibrium but the release rate controlled the efficacy of the system.

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