Green Synthesis of Carbon Quantum Dots from Buttermilk for Antimicrobial Preservation and Shelf-Life Enhancement of Paneer

The major objective of this study was to synthesize and characterize carbon quantum dots (CQDs) from buttermilk using hydrothermal technique and to evaluate their antimicrobial efficacy as a natural preservative for paneer. The sample with the highest fluorescence intensity among the three prepared samples (10%, 20%, and 30% buttermilk dilution) was chosen for in-depth characterization. The buttermilk-derived CQDs (BM-CQDs) were quasi-spherical with an average size of 6.14 nm as observed by High Resolution Transmission Electron Microscopy. Ultraviolet-Visible spectroscopy showed an absorption peak at 283 nm, corresponding to the π-π* transition of aromatic C=C bonds, while photoluminescence (PL) analysis revealed a strong emission peak at 422 nm when excited at 340 nm. Elemental analysis indicated the presence of C (67 %), N (6.1 %), and O (14 %), as confirmed by the Energy Dispersive X-ray, suggesting natural doping. X-ray Diffraction analysis revealed a broad peak at ~20° (2θ), indicative of amorphous nature, and Fourier Transform-Infrared spectroscopy confirmed the presence of -OH, -NH, -C=O, and other functional groups. The developed BM-CQDs were used for enhancing the shelf-life of paneer. Paneer samples treated with 2,500 mg/L and 5,000 mg/L BM-CQDs showed a significant reduction in microbial counts, total viable, coliform, and yeast and mould count compared to untreated control during storage study. Twenty-one days increase in the shelf-life of paneer was recorded with the BM-CQDs. These findings highlight the potential of BM-CQDs as a novel, eco-friendly solution for dairy products preservation and shelf-life enhancement, aligning with clean-label food trends and waste valorization strategies.