Photothermal-responsive multifunctional silk fibroin-based composite film with dialdehyde cellulose and nanoparticles for extending shelf life of blueberries.

Food safety and environmental concerns drive the search for innovative food packaging. This study presented the development of a novel degradable multifunctional packaging film based on silk fibroin (SF) integrated with dialdehyde cellulose nanocrystals (DCNC) derived from Rosa roxburghii pomace (RRP) and epigallocatechin gallate (EGCG)-based photothermal nanoparticles (NPs). DCNC enhanced mechanical properties of films via Schiff base cross-linking with SF. EGCG NPs were synthesized through a Mannich reaction and functionalized with tannic acid/Fe3+ layers to confer photothermal sterilization capabilities. Results demonstrated that EGCG NPs and DCNC improved tensile strength and reduced water vapor permeability by forming a dense hydrogen network. The composite films exhibited excellent photothermal conversion under near-infrared (NIR) irradiation, achieving an 82 °C at 40 mg NPs loading. Moreover, photothermal stimulation induced the release of EGCG nanoparticles from the films, which conferred remarkable antioxidant and antibacterial activities. Notably, the SF-40 film achieved 100% inhibition against E. coli under NIR irradiation. Blueberry preservation tests further verified that the films could effectively reduce decay rate and weight loss, and prolong the shelf life of fruits. Additionally, the SF-based films exhibited rapid biodegradation within 21 days. This work provided a sustainable strategy for converting agricultural waste into high-performance packaging materials, combining antibacterial, antioxidant, and photo-radiation enhanced antibacterial activity properties to address food safety and environmental challenges.