Effect of orange peel carbon dot immobilized titanium-based metal-organic framework on buckwheat starch/chitosan films and their preservation performance for grapes.

The growing demand for sustainable and active food-packaging materials has encouraged the development of biodegradable films with enhanced functional properties to replace conventional petroleum-based plastics. Orange-peel-derived carbon dots (OPCDs) were synthesised and immobilized onto a titanium-based metal-organic framework to produce a robust hybrid nanofiller (OPCD@Ti-MOF) for incorporation into buckwheat starch/chitosan (BS/CH) biopolymer films for food-packaging applications. Firstly, The OPCD@Ti-MOF was synthesised using solvothermal-assisted mechanical stirring, and the TEM, FTIR, and fluorescent techniques confirm the successful synthesis of nano-fillers. They exhibited excellent antioxidant and antibacterial properties. These were subsequently incorporated in 1, 2, and 4 wt% into buckwheat starch/chitosan (BS/CH) biopolymer films. The findings revealed that insertion of OPCDs increased the hydrophilicity of films, but addition of a combined composite OPCD@Ti-MOF induced hydrophobicity and improved the functional activity of films. The optimized S5 film with BS/CH/OPCD@Ti-MOF (2 wt%) demonstrated strong antibacterial ability against S. aureus and E. coli and, with inhibition zones of 21.2 mm and 23.1 mm, respectively, as well as excellent antioxidant activity, achieving 77.30% ABTS• + and 87.80% DPPH• radical scavenging efficiency. Furthermore, S5 film exhibited improved mechanical attributes and ultraviolet light-blocking ability (95.70% of UV-B and 84.71% of UV-A). Cytotoxicity studies confirmed their non-toxic behavior, and soil burial tests confirmed their biodegradable nature. When applied to green grapes, the S5 film enhanced the shelf life of green grapes to 25 days at 4 °C. These findings demonstrate that the synthesised films are promising biodegradable active packaging materials for improving food preservation and reducing dependence on conventional plastic packaging.