Carbon quantum dots-based antifungal coating film for active packaging application of avocado

This study investigated the applicability of carbon dots (CDs) as a functional filler for producing active food packaging films. CDs were synthesized by a one-pot hydrothermal method using glucose as the carbon source. The CDs were used to prepare chitosan/gelatin (Chi/Gel)-based composite films. The addition of CDs increased the UV blocking property of the film by 99% without significant change in mechanical properties, water vapor permeability (WVP), and water contact angle (WCA). In addition, the CDs-added composite films showed potent antioxidant activity. The composite film generates reactive oxygen species (ROS) and exhibits high antibacterial activity against pathogenic bacteria, showing 100% destruction of L. monocytogenes and E. coli. The composite film also exhibited high antifungal activity against mold (Aspergillus flavus and Colletotrichum orbiculare) and had negligible cytotoxicity to L929 cells even after long-term exposure of 72 h. The chitosan/gelatin/CDs-film coating effectively inhibited the growth of mold on the surface of avocados and extended the fruit shelf life by more than 14 days. The CDs are likely to be a value-added, low-cost, and safe, functional nanofiller for preparing functional films for active packaging applications.