Chitosan/Carboxymethyl cellulose edible coating loaded with aggregation-induced emission photosensitizers: A robust yet biocompatible antimicrobial film for Litchi preservation

Abstract

Litchi deteriorates rapidly postharvest due to high moisture, enzymatic browning, and microbes. In this work, an eco-friendly, antimicrobial aggregation-induced emission photosensitizers-loaded chitosan/carboxymethyl cellulose (AIE-CS/CMC) coating film was developed and validated to significantly delayed pericarp browning, inhibited spoilage and retained most of the nutrients, extending litchi's shelf life by approximately eight days compared with the untreated water-blank control. These effects were attributed to the robust yet biocompatible photodynamic sterilization of AIE-CS/CMC coating film, coupled with excellent gas barrier and moisture control. Importantly, this coating film killed more than 95% Escherichia coli, Pseudomonas fluorescens, Lactobacillus acidophilus, Staphylococcus aureus and Penicillium in suspension (106 CFU/mL), with outstanding mechanical performance (6.2 MPa tensile strength and 34.3% tensile elongation), low water vapor transmission rate (0.91 × 10−11 g·m−1·s−1·Pa−1), low ultraviolet light transmission rate (46.6% at 300 nm) and high water contact angle (78.48°). This AIE-CS/CMC coating could be considered a highly efficient postharvest quality management of litchi fruits.