Fabrication and application of a Dendrobium officinale polysaccharide-based active film incorporated with carbon dots and anthocyanins for shrimp preservation.

This study developed an intelligent active packaging film based on Dendrobium officinale polysaccharides (DOP), incorporating copper-doped carbon dots (Cu-CD) derived from the residue of DOP extraction and anthocyanins (AMA) extracted from Aronia melanocarpa. To clarify the fundamental physicochemical properties of DOP and AMA, both were systematically characterized. For DOP, the molecular weight, monosaccharide composition, total sugar content, and in vitro antioxidant activity were determined. For AMA, the total anthocyanin content and antioxidant activity were measured. On this basis, the effects of these two additives on the physical, functional, and structural properties of the composite films were systematically evaluated. The incorporation of Cu-CD (1% and 3%) significantly improved the mechanical performance of the films (P < 0.05), which also exhibited excellent UV-blocking ability, high antioxidant capacity, and antimicrobial efficacy confirmed by shrimp preservation experiments; the film-forming solutions additionally showed antibacterial potential in agar diffusion screening. The copper ion migration from the Cu-CD-containing films was found to be below the corresponding benchmark values under the tested conditions. When shrimp were stored at 4 °C for 10 days, films containing AMA and Cu-CD effectively reduced spoilage and extended shelf life. Meanwhile, their color shifted from red to purple and ultimately purple-black, enabling real-time indication of freshness. Therefore, DOPs/AMA/Cu-CD composite films show great promise as bio-based food-packaging materials, capable of indicating freshness and prolonging product shelf life.