Thermo-/pH-responsive preservative delivery based on TEMPO cellulose nanofiber/cationic copolymer hydrogel film in fruit packaging

Hydrogels have great potential in food packaging. However, stimuli-responsive preservative delivery-based hydrogels for emerging active packaging have not yet been explored. Herein, Unprecedented pH/temperature-responsive hydrogel films for emerging active climacteric fruit packaging were developed based on TEMPO-oxidized nanofibrillated cellulose (TOCNFs) from wheat straw with food-grade cationic-modified poly(N-isopropyl acrylamide-co-acrylamide) (CPNIPAM-AM). TOCNF incorporation into CPNIPAM-AM revealed desirable enhancement of characterization, antimicrobial properties, and pH/thermal-responsive behaviour. In-vitro delivery and release mechanism studies with natamycin revealed the fastest release rates in preferred low pH media, up to 32.1 times higher than that under neutral conditions via anomalous diffusion. Applying a thermal stimulus increased natamycin release rates, providing 1.5-21% gradual-additional pulses by Fickian diffusion. The final hydrogel film showed efficient decay control in response to stimuli of the climacteric fruit environment with safe, recyclable, and feasible application demonstrating the significant potential to be used as an alternative-sustainable material for stimuli-triggered preservative delivery in climacteric fruit packaging.