NIR-triggered spatiotemporal control of cinnamaldehyde release in antibacterial pickering emulsion hydrogel for prolonged preservation of table grapes

Food spoilage caused by microbial proliferation and moisture loss remains a critical challenge in postharvest management. This study proposes a smart hydrogel system integrating photothermal-responsive Pickering emulsions and thermo-sensitive biopolymers to achieve on-demand antimicrobial release and water retention. The Pickering emulsion, stabilized by indocyanine green (ICG)-loaded halloysite nanotubes (HNTs), serves as an antimicrobial depot of cinnamaldehyde (Cin). Under near-infrared (NIR) irradiation, ICG converts light energy into heat, triggering both thermal-enhanced Cin volatilization and sol-gel transition of the κ-carrageenan/gelatin (CG) hydrogel matrix. This dual-action mechanism enables: (i) Spatiotemporal control: NIR exposure achieves precise Cin release, with cumulative release increasing to 21.5 %; (ii) Dual-mode antibacterial efficacy: The system exhibits a 3.12 cm inhibition zone against S. aureus and complete suppression of Penicillium expansum growth through combined contact and vapor-phase antimicrobial activity. (iii) Superior preservation performance: Grapes packaged with the hydrogel maintain 98.92 % initial weight after 14 days, with retained firmness, stable pH, and minimal soluble solids loss. By synergizing photothermal conversion, thermal-responsive hydrogel dynamics, and natural antimicrobials, this work establishes a non-contact preservation platform that extends grape shelf life by 250 %, demonstrating significant potential for intelligent food packaging applications.