Antimicrobial keratin-based sustainable food packaging films reinforced with citric acid-modified cellulose nanocrystals

Sustainable food packaging films play a crucial role in maintaining the freshness and quality of the food, while prioritizing environmental sustainability. In this paper, a transparent film with antibacterial properties and excellent tensile property was prepared utilizing keratin extracted from waste chicken feathers, combined with citric acid-modified cellulose nanocrystals (CNC-CA). The film exhibited an elongation at break of 209%, highlighting its substantial potential for food packaging applications and addressing the brittleness problem associated with keratin-based films. Microstructural analysis revealed that, the network formed by keratin and CNC-CA with the presence of extensive sliding hydrogen bonds and the transformation of keratin's secondary structure from α-helix to β-sheet were pivotal in enhancing the tensile strength of the Keratin/CNC-CA film. The citric acid not only act as crosslinkers, but also contribute to the sustained antimicrobial and antioxidant capabilities of the prepared Keratin/CNC-CA film, eliminating the need for adding chemically synthesized antimicrobial agents. The high stretchability of the Keratin/CNC-CA film facilitates the secure packaging of loose food items, effectively preserving freshness by minimizing air exposure, and could be degraded rapidly upon disposal, converting into organic fertilizer in the soil, and thereby mitigating the environmental problems induced by conventional plastic packaging films. This work highlights the great potential of waste biomass-derived material keratin in preparation of functional films with antibacterial property, offering promising application prospects in food packaging contexts.