Ulva lactuca polysaccharide composite film: Preparation and application in large yellow croaker (Larimichthys crocea) preservation

To develop eco-friendly and efficient preservation materials for aquatic products, a composite film (ULP) was fabricated from Ulva lactuca polysaccharide (PULP), sodium alginate, glycerol, and gelatin. The film exhibited excellent film-forming ability, mechanical strength, and barrier properties, attributed to enhanced hydrogen bonding and hydrophobic interactions. In vitro assays showed that PULP possessed radical scavenging activity and inhibited Escherichia coli and Staphylococcus aureus . When applied to large yellow croaker ( Larimichthys crocea ) fillets, the ULP significantly delayed quality deterioration. It reduced drip loss by 35.16%, slowed color change, and lowered the accumulation of total volatile basic nitrogen (24.03%) and lipid oxidation (13.79%) by the end of storage, while suppressing microbial growth due to the sustained release of active components. Flavor analysis revealed that the ULP maintained higher levels of fresh-flavor hexanal and reduced spoilage-related trimethylamine. Molecular docking indicated that both compounds primarily bind to olfactory receptors (OR2W1, OR10K1, OR10S1) via hydrophobic interactions, with hexanal showing higher binding affinity than trimethylamine. These results suggest that ULP preserves fresh flavor by inhibiting spoilage bacteria and delaying hexanal degradation. This research demonstrates the promise of ULP as a bioactive packaging material for seafood preservation, providing a new approach for utilizing marine algae. • A composite film (ULP) was developed from marine Ulva lactuca polysaccharide. • The ULP showed excellent mechanical, antioxidant, and antibacterial properties. • The ULP prolonged large yellow croaker shelf life to 10 days at 4 °C. • The ULP is derived from natural marine resources and is non-toxic.