Chitosan-based multifunctional coating combined with sulfur quantum dots to prevent Listeria contamination of enoki mushrooms

A chitosan-based multifunctional coating solution was prepared by adding sulfur quantum dots (SQDs) to secure the safety of enoki mushrooms by circumventing L. monocytogenes infection. The chitosan-based coating solutions with various concentrations of SQDs (0, 1, 2, and 3 wt% with respect to chitosan) were cast into flexible films to test their physicochemical and functional characteristics. The SQD-added films showed excellent UV-blocking properties, but their transparency was significantly decreased. The incorporation of SQDs significantly enhanced the mechanical stability (by 15.8-29.7%) without significantly changing the chitosan film's water vapor transmission characteristics and considerably increased the antioxidant activities (up to 273% and 169% of DPPH and ABTS radical scavenging efficacies, respectively). The SQD-added film showed significantly increased antimicrobial activity against E. coli and L. monocytogenes. When the coating solution was applied to the enoki mushrooms, no substantial change was observed in the appearance of the coated mushrooms. The chitosan/ SQD3% coating solution effectively prevented Listeria contamination of enoki mushrooms and eradicated 100% of the inoculated bacterial colonies within 6 days.