Release of coumarin incorporated into chitosan-gelatin irradiated films

Abstract : Chitosan and fish gelatin were used to formulate active biobased films containing an antioxidant (coumarin). After drying, the films were irradiated at 40 and 60 kGy using an electron beam accelerator. The effect of irradiation on the film properties as well as the coumarin release mechanism were investigated and compared with the control. Electron Spin Resonance (ESR) revealed free radical formation during irradiation in films containing coumarin. Antioxidant addition and/or irradiation treatment at a dose of 60 kGy resulted in a shift of amide A and amide B peaks. Furthermore a shift of amide II band was only observed for the control film at the same dose. Irradiation allowed improving the thermal stability of the control films. Both irradiation process and addition of coumarin increased the surface wettability (increase of the polar component of the surface tension). From the water barrier analysis, neither irradiation nor coumarin addition influenced the permeability at the lower RH gradient used (0-30% RH). Using the higher RH gradient (30-84%) induced a rise of the WVP of all films (containing or not coumarin) after irradiation treatment. At 60 kGy, the tensile strength of only the control films increased significantly. Considering coumarin release from the film in aqueous medium, the apparent diffusion coefficient of coumarin is two times reduced after irradiation. Irradiation also allowed to better protect the incorporated antioxidant. Indeed, the amount of coumarin in the non-irradiated film was significantly lowered compared to the initial quantity, which is probably due to chemical reactivity.