Incorporating tannin onto regenerated cellulose film towards sustainable active packaging

Packaging materials from biodegradable and renewable natural resources have received more and more attention. In this work, novel tannin-cellulose films with high antioxidant and mechanical properties were prepared for sustainable active food packaging. The cotton linter dissolving pulp was dissolved in ionic liquid (AmimCl) and regenerated in water to form cellulose film (CF). CF was periodate oxidized to get dialdehyde cellulose film (DACF) with aldehyde groups on the surface and then immersed in tannin solution to prepare tannin cellulose films (TCFs). Varied amounts of tannin were covalently bonded on the film surface by reaction between tannin and aldehyde groups on DACF. The obtained TCFs demonstrated high antioxidant and UV blocking properties. With the increase of tannin loading on the film surface, the antioxidant activity of TCFs increased gradually. The incorporation of tannin improved the hydrophobicity and water vapor barrier properties of the cellulose film. The dry tensile strength of TCFs decreased, while the wet tensile strength and strain at break increased significantly, compared with those of pure cellulose film. TCF with a tannin loading of 19.2% displayed a wet tensile strength of 26.8 MPa and strain at break of 25.6%. The wet tensile strength was comparable to some commercial packaging films in the dry state. The obtained TCFs with high antioxidatnt, UV blocking and mechanical properties exhibite enormous application potential in active food packaging.