Exopolysaccharide-rosmarinic acid complex as a phosphate replacer: dual improvement of oxidative stability and gel properties in myofibrillar proteins

Under a clean-label strategy, this study developed a non-covalent extracellular polysaccharide (EPS)-rosmarinic acid (RA) complex (EPS-RA) via laccase-catalyzed conjugation to enhance natural phosphate alternatives. FTIR, XRD and NMR confirmed hydrogen bonding and van der Waals interactions between EPS and RA. EPS-RA showed improved thermal stability and viscosity over EPS. Using oxidized pork myofibrillar protein (MP) as a model, sodium pyrophosphate (PP) or EPS-RA alone reduced carbonyl formation, limited particle growth and improved MP gel properties, while their combination produced the strongest protection. PP mainly provided ionic regulation and gel strengthening, whereas EPS-RA offered stronger antioxidant activity, protected secondary structure and increased water-holding capacity, allowing partial replacement of phosphates. Their synergy markedly enhanced oxidative stability and gel quality of MP, supporting the design of low-phosphorus meat products. Density functional theory calculations further elucidated the binding features and free-radical scavenging mechanism of EPS-RA. • Laccase-catalyzed preparation of the EPS-RA complex via non-covalent interactions. • Compared with pristine EPS, EPS-RA exhibits enhanced antioxidant activity, thermal stability, and viscosity. • EPS-RA can inhibit myofibrillar protein oxidation, protect protein structure, and improve gel properties. • Density functional theory clarifies its free radical scavenging mechanism; EPS-RA can partially replace sodium pyrophosphate, providing support for the development of low-phosphorus meat products.