Nanocellulose-tannin films: From trees to sustainable active packaging

Cellulose nanofibrils and condensed tannins were chosen to prepare a strong, sustainable packaging material. Cellulose nanofibrils provided the physical and mechanical requirements, while the tannin was incorporated due to its antioxidant properties. Herein, an easy, one-step method was designed to prepare a film containing 190 mg/g of active molecules. The incorporation of tannin into the cellulose matrix was carried out through the mechanical fibrillation of cellulose pulp and tannin mixtures. The tanninincorporated cellulose films presented high density and improved surface hydrophobicity, which resulted in a 6-fold enhancement in their air-barrier properties. A slow release of antioxidant components was verified upon soaking, as well as good resistance to several solvents. The mechanical features of the cellulose matrix were not significantly affected by the incorporation of such phenolic molecules. These properties are key factors to put forward the utilization of tannin-added films as a valid green, nontoxic packaging material for food and pharmaceutical products.