Modeling of the release kinetics of phenolic acids embedded in gelatin/chitosan bioactive-packaging films: Influence of both water activity and viscosity of the food simulant on the film structure and antioxidant activity.

Hydrocolloid-based films containing natural phenolic antioxidants (gallic and trans-cinnamic acids at 5% w/wt of polymers) embedded in a gelatin/chitosan matrix were designed as sustainable active packaging. This work deals with characterizing the release mechanisms of the phenolic acids from the films immersed into food simulants (sugar or polyol solutions) having different water activities and viscosities. The films containing gallic acid exhibited higher antioxidant activities than the trans-cinnamic acid films. The use of sucrose or glycerol to reduce the water activity (aw) both decreases the iron chelating power (antioxidant) and the E Coli growth (antimicrobial). Interactions involved between macromolecules (chitosan and gelatin) and phenolic compounds influence the release kinetic parameters (diffusivity, convection and partition coefficients) that were studied according to the nature of solute, the water activity and the viscosity of the release media. Thermal analysis (TGA and DSC) revealed a plasticization by both sucrose and glycerol, which entered the film.