Aggregation-induced emission garlic peel carbon dots infused-carrageenan/whey protein emulsion for apple spoilage biosensing

This study introduces a novel, dual-functional food preservation system by integrating carbon dots (CDs) synthesized from sustainable red garlic peels (RP) into a biopolymer-based edible coating. Our findings demonstrate that this CDs-infused emulsion provides superior preservation for fresh apple pieces, extending their shelf life to six days compared to the three-day shelf life provided by a conventional whey protein-carrageenan control. Importantly, the CDs-infused coating provided a unique, naked-eye colorimetric response to spoilage, turning red as degradation began, in contrast to the black, opaque spoilage of the control. While the CDs-infused emulsion displayed lower direct antimicrobial efficacy compared to the control, its superior performance in apple preservation (6 days vs. 3 days) suggests that the shelf-life extension is primarily governed by the inhibition of enzymatic pathways and oxidative stress, rather than purely biocidal activity. Colorimetric contour mapping and CIE color coordinate analysis showed a consistent and specific optical response to microbial contamination. The uncontaminated emulsion had a baseline coordinate of (0.178, 0.152), which shifted distinctly upon exposure to E. coli (0.178, 0.171), S. aureus (0.174, 0.143), and C. albicans (0.174, 0.145). This demonstrates the system’s ability to differentiate between various classes of microbial contaminants. Furthermore, fluorescence spectroscopy confirmed a powerful Aggregation-Induced Emission (AIE) mechanism, where the presence of microbes significantly enhanced the fluorescence intensity, with a unique response for each species. Our work establishes a new paradigm for designing active, sustainable food packaging materials that not only extend shelf life but also provide a practical, real-time visual indicator of apple freshness.