Release of active compounds from agar and agar–gelatin films with green tea extract

Active biodegradable films based on agar and agar–fish gelatin were developed by the incorporation of green tea aqueous extract to the film forming solution. The effect of the partial replacement of agar by fish skin gelatin as well as the addition of the green tea extract on the physical properties of the resultant films was evaluated. Special attention was given to the release of antioxidant and antimicrobial compounds from the agar film matrices with and without gelatin. Agar–gelatin films were less resistant and more deformable than agar films. The inclusion of green tea extract decreased tensile strength and elongation at break in both agar and agar–gelatin films. Water vapour permeability and water resistance was not affected either by the replacement of agar by gelatin or the addition of green tea extract, but the water solubility noticeably increased in the films containing green tea extract. The presence of gelatin in the agar–green tea matrix film hindered the release of total phenolic compounds, catechins and flavonols in water. As a consequence, the antioxidant power released by the films was lower in the case of films containing gelatin. However, the antimicrobial activity of the films was not affected by the presence of gelatin.