Gelatin films reinforced by tannin-nanocellulose microgel with improved mechanical and barrier properties for sustainable active food packaging

In this study, reactive tannin-nanocellulose (TANC) microgels, prepared using dialdehyde nanocellulose and tannin through the condensation reaction, were incorporated into gelatin matrix to fabricate GE-TANC films for the potential application as active food packaging materials. AFM, FT-IR, XRD, and TG analysis were employed for characterization of TANCs and the composite films. AFM images and FT-IR analysis confirmed the successful crosslinking of nanocellulose with tannin. Their surface hydrophilicity, UV-blocking capability, antioxidant activity and mechanical properties were measured to investigate the impact of TANC microgels on the film properties. The tannin-containing films displayed excellent antioxidant and UV-blocking properties, maximally scavenging 79% of DPPH free radicals and absorbing 98% of ultraviolet light. The surface hydrophilicity, water vapor transmission rate (WVTR) and water solubility of the composite films decreased compared to those of the neat gelatin film, resulting from the formation of more chemical and physical crosslinkings within the film. The tensile strength tripled from 40 MPa to 108 MPa, and the elongation at break increased from 3.87% to 6.28% with only 5% of TANC2. The GE-TANC films in this work demonstrated high mechanical properties, oxidation and UV resistance, and thus have a prospective application as the sustainable active food packaging materials.