Use of tannins to enhance the functional properties of protein based films

In this study, three tannins from different sources have been used (from white peel grape (W), red peel grape (R) and from oak bark (O)) to obtain active films based on proteins (caseinate and gelatin) on the basis of their natural origin and potential antioxidant and antimicrobial activity. Films were obtained in two different ways: monolayer films, by homogeneously blending the tannins with the proteins and bilayer films, by coating the previously obtained protein film with the different tannin solutions. The microstructural, physicochemical characterisation as well as the antioxidant and antimicrobial activities of the films were analysed. The interactions developed between tannins and protein matrices determined the physico-chemical properties of the films. Significant changes were only observed in tannin-caseinate films, due to the establishment of hydrogen bonding and hydrophobic interactions, especially when using the tannin with the greatest phenolic content (W). Thus, the W tannin caseinate based films turned thicker, with markedly improved (p