Development of smart food packaging from bread waste-derived starch and carbon quantum dots

This study explores an innovative approach to transforming leftover bread, a major source of food waste, into eco-friendly packaging materials. Using the ultrasound-assisted hydrothermal method and a chemical-free approach, carbon quantum dots (QDs) and starch (ST) were derived from leftover bread. Smart films were then developed by blending ST, glycerol, and QDs (1 % or 3 wt% of ST) and alizarin (AL), using solvent casting. QDs exhibited UV-barrier, photoluminescent, antioxidant activity (79.13 % DPPH radical scavenging), and low toxicity to murine fibroblasts below 200 µg/mL. Their inclusion improved film plasticity, increased elongation by 59 %, enhanced the water vapor barrier, and raised surface hydrophobicity. The films showed antibacterial effects, inhibiting E. coli by 47.77 % and S. aureus by 97.82 %. Interactions between QDs and AL led to a reduced visual color change in the colorimetric films in response to ammonia and acetic acid vapors; however, they enhanced the films' fluorescent properties. This study introduces a sustainable biorefinery strategy to upcycle bread waste into smart packaging, reducing waste and contributing to food spoilage monitoring.