Effects of sustained release of tea polyphenols from a bacterial cellulose-based coating to prolong shelf-life of fresh walnuts

Fresh walnuts are highly perishable due to high moisture and unsaturated lipid contents. A multifunctional coating was developed by grafting glycerol onto oxidized bacterial cellulose to form a stable nanonetwork and incorporating tea polyphenols. Structural analyses revealed a compact network with improved crystallinity and barrier integrity, supporting sustained release of tea polyphenols. The coating exhibited strong antioxidant activity (72% scavenging) and broad-spectrum antibacterial efficacy (inhibition rates up to 97.8%). Cytocompatibility assays using human gastric epithelial cells confirmed excellent biocompatibility. When applied to fresh walnuts, the coating reduced moisture loss (maintaining a moisture content of 23.4%), delayed lipid oxidation (suppressing acid value to 2.3 mg KOH·g −1 ), and preserved total phenolic content (3.52 mg/g) after 60 days. Furthermore, it effectively inhibited microbial growth, maintaining the total viable count at 3.8 log CFU/g, significantly below the safety threshold. These results demonstrate a green, effective strategy for sustainable preservation of perishable nuts.