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

Sprayable coating forms film in seconds and is easily washable. • Scavenges >89% free radicals and inhibits >98.9% of bacteria. • Extends fruit shelf life 2–4 times while preserving nutrients. • Safe for consumers with final selenium residue under 0.15 mg/kg. 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. Download: Download high-res image (140KB) Download: Download full-size image