Emulsions stabilized by high-acyl gellan gum/sodium caseinate complexes: characterization, stability, and application for lutein delivery

Lutein (LU), a lipophilic bioactive compound with well-documented health benefits, exhibits poor stability and low bioaccessibility, which limit its application in functional foods. This study investigates the potential of high-acyl gellan gum (HA) to enhance the protection and delivery of LU in sodium caseinate (SC)-stabilized oil-in-water emulsion. Two types of LU-loaded emulsions were prepared; SC–LU emulsion and the HA-stabilized version (HA–SC–LU emulsion). Both systems were subjected to various environmental stresses, including variations in pH, temperature, and ionic strength, during storage. The physical stability, oxidative stability, LU retention, and in vitro digestibility of the emulsions were systematically evaluated. Results indicate that the incorporation of HA significantly improves the physical stability of the emulsions by reducing the instability index and preventing droplet aggregation. In addition, HA enhances LU retention under all tested stress conditions and effectively inhibits lipid and protein oxidations over a 28-day storage period. Furthermore, in vitro digestion studies reveal that the HA–SC–LU emulsion achieves a higher rate of free fatty acid release and significantly improves LU bioaccessibility (77.32%) compared to the SC–LU control (20.04%). Overall, these findings highlight that HA is an effective stabilizer for enhancing the physicochemical stability and bioaccessibility of LU in protein-based emulsion delivery systems, demonstrating promising potential for applications in functional foods and nutraceuticals. • HA markedly enhanced the physical and oxidative stability of SC emulsions. • HA effectively prevents emulsion aggregation and degradation under environmental stress. • Incorporation of HA improved lutein retention and suppressed lipid and protein oxidation during storage. • The HA-SC composite emulsion increased lutein bioaccessibility in vitro digestion.