Double network hydrogel coating improved avocado freshness preservation: Preparation, testing and mechanism

This study aims to design a functional double network hydrogel (DN) coating using a simple, cost-effective process for fruit preservation and to explore a novel approach employing edible DN for avocado storage. The DN was fabricated by combining amyloid fiber (AF) with epigallocatechin gallate (EGCG) and chitosan (CS), cross-linked using natural genipin (GP). The two biopolymer networks were optimized in specific proportion to form a homogeneous microstructure, which was applied to avocado surface via a liquid-solid phase transition to enhance storability at ambient temperature. The results demonstrated that the DN coating exhibited significantly lower water vapor transmittance (389.65 ± 3.62 g m⁻²d⁻¹) and complete UV-light blockage (0% transmittance). Additionally, it showed a markedly higher free radical scavenging capacity (106.97%–116.20%) compared to CS and demonstrated strong antimicrobial efficacy against pathogens, including Staphylococcus aureus (51.00%), Escherichia coli (62.12%), Listeria (30.60%) and Pseudomonas aeruginosa (66.24%). Moreover, the DN coating achieved the desired performance in avocado preservation. Avocados coated with DN extended their shelf life to 12 d while maintaining fruit quality. During storage, the DN coating inhibited fruit respiration, reduced ethylene release, and enhanced the activity of antioxidant enzymes (SOD and POD) in vivo. This study demonstrates that the DN coating as a promising strategy for food preservation due to its simplicity, safety, and effectiveness, offering significant potential for practical applications in the food industry.