Effects of coffee bean types on the characteristics of carbon dots and their use for manufacturing cellulose nanofibers-based films for active packaging of meat

Abstract

CDs (carbon dots) were made through a hydrothermal process using three different types of coffee grounds (raw, roasted, and spent), and their physicochemical and optical properties were thoroughly studied. CNF (cellulose nanofibers)-based active packaging films were made and characterized by incorporating the CDs. The introduction of CDs improved the tensile strength of the CNF-based films by 26.1% and provided excellent UV-blocking ability by blocking 98.8% of UV-B and 87.4% of UV-A without sacrificing the film’s transparency. The CD-loaded CNF films showed strong antioxidant properties with ABTS radical and DPPH radical removal rates of 98.2% and 78.8%, respectively. Additionally, these films showed effective antimicrobial potential and significantly reduced the progress of E. coli and L. monocytogenes after 12 h of exposure. Packaging tests were performed at 4 °C for 21 days, which depicted that minced pork packaged with the CD-added CNF films preserves the quality of packaged meat in terms of appearance, pH, total viable colonies, and TBARS (thiobarbituric acid reactive substances). It is expected that manufacturing functional fillers (CDs) using waste resources generated in the food industry and developing active packaging films using them will not only extend the shelf life of packaged foods but also help in resource recycling and solving environmental problems.