A sprayable, washable carboxymethyl chitosan-based selenium nanocomposite coating for antibacterial and nutrient preservation in postharvest fruits.

Postharvest fruits are highly susceptible to spoilage, whereas traditional plastic packaging poses environmental concerns. This study presents a sprayable, water-washable carboxymethyl chitosan-based nanocomposite coating fabricated via a hydrogen bond-electrostatic self-assembly strategy. By incorporating epigallocatechin gallate-glucan‑selenium nanoparticles (E-G-SeNPs) and tannic acid, the coating demonstrates exceptional preservation efficacy and biosafety. It forms a film within seconds upon spraying, offering sustained release of E-G-SeNPs and enhanced antioxidant activity, with 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2-Azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS·+) radical scavenging rates of 94.1% and 89.7%, respectively. The coating demonstrates broad-spectrum antibacterial activity, inhibiting over 98.9% of both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria. It significantly extends shelf life (by 2- to 4- fold), and can be easily removed by water rinsing, with minimal selenium residue (<0.15 mg/kg), ensuring that consumer daily selenium residue remains strictly within established dietary safety limits. This low-cost, water-washable, and highly versatile coating offers a sustainable solution for postharvest fruit preservation.