Multifunctional ammonia-responsive starch composites engineered by deep eutectic solvent-cellulose synergy and...

In recent years, smart responsive labels based on natural pigments have attracted considerable attention for monitoring food freshness, but their application has been limited by issues such as complex extraction processes and poor stability. Therefore, this study utilized a deep eutectic solvent (DES) and cellulose-reinforced hydroxypropyl starch (St) as the matrix, and loaded it with Cu-MOF-74, which possesses both ammonia-sensitive response and antibacterial functions, to construct a green, stable, and high-performance intelligent responsive film. The synergistic effect of choline chloride-urea-glycerol (ChCl-U-G) and cellulose improved the toughness of the starch matrix (elongation at break increased by 4.18 times), and the material exhibited good biodegradability (over 85% degradation within 14 days). Comprehensive characterization showed that the introduction of DES and cellulose disrupted the original hydrogen bond network of hydroxypropyl starch, as reflected by a red shift in the -OH stretching vibration (Δν = 70 cm^-1), a decrease in crystallinity of 18.74%, and a decrease in ΔH of 24.39%. The Cu₈/C_1.5ChCl-U-G-St film exhibited strong antibacterial properties (>85% inhibition) and ammonia sensitivity (ΔE > 5 within 5 min). In application experiments, the film enabled real-time visual monitoring of pork freshness at 4 °C and 25 °C while also exhibiting a preservation effect. Reduced density gradient (RDG) and binding energy calculations revealed strong intermolecular interactions (-181.45 kcal/mol) within the cellulose, ChCl-U-G, and St systems. This work provides both theoretical and practical insights into the design of intelligent biomass materials for real-time food freshness monitoring.