Gelatin-based composite film integrated with nanocellulose and extract-metal complex derived from coffee leaf for sustainable and active food packaging

Gelatin (GEL) is widely used in food packaging due to its excellent film-forming ability, non-toxicity, biodegradability, and biocompatibility. However, pure GEL films suffer from poor mechanical strength, high water sensitivity, and lack antibacterial properties, limiting their suitability for food packaging applications. In this study, we incorporated dialdehyde cellulose nanocrystal (DCNC) derived from coffee leaves as cross-linkable nanofillers and a coffee leaf extract-Fe³⁺ complex (CFe) as a functional additive into GEL to develop active food packaging composite films. We investigated the effects of varying CFe content on the microstructure and performance of films. The addition of 1 wt% CFe enhanced the entanglement and intermolecular interactions among the film-forming components, resulting in a dense and continuous microstructure. This led to significant improvements in UV-light shielding, mechanical strength, water solubility, water vapor and oxygen barrier properties of the GEL-based composite films. Owing to the excellent photothermal conversion capability of CFe, the composite films exhibited strong antibacterial activity against S. aureus and E. coli, with an antibacterial efficiency exceeding 90%. Additionally, the inclusion of CFe imparted good antioxidant properties to the composite films. Packaging application tests further demonstrated that the functional films, when assisted by 808 nm near-infrared (NIR) laser irradiation, effectively slowed the quality deterioration of fresh pork, extending its shelf-life to 8 days under 4 °C storage. These findings suggest that the developed composite films hold significant promise for use in food packaging.