Synergistic stabilization of DHA nanoemulsions using sodium caseinate-gum Arabic Maillard conjugates

As a delivery system, the nanoemulsion significantly enhanced the stability of encapsulated DHA oil, crucial for achieving high bioavailability. DHA algal oil nanoemulsions were fabricated with sodium caseinate (CS), gum arabic (GA), a CS-GA Maillard conjugate, and whey protein isolate (WPI). They were stored at 4°C and 25°C for 35 days, during which changes in particle size, polydispersity index (PDI), zeta potential, free radical scavenging capacity, oxidation products, and flavor profiles were evaluated. After 28 days at 4°C, GA nanoemulsion (GA-NE) was the least stable, showing an 88.3% increase in particle size. In contrast, the CS-GA conjugate-based nanoemulsion (CS-GA-NE) showed the best stability, with only a 9.6% increase. After 35 days at 25°C, CS-GA-NE retained a DPPH scavenging capacity of 152.34 μmol TE/100g. Its peroxide value (POV) was 710 μmol/100g and thiobarbituric acid reactive substances (TBARS) was 0.11 mg/100g; both values were significantly lower than those of the other formulations. GC-MS analysis indicated that the CS-GA interfacial layer suppressed lipid oxidation via synergistic electrostatic repulsion and steric hindrance, and also reduced the formation of off-flavor aldehydes and ketones. These findings showed that CS-GA-NE possessed excellent physical stability and antioxidant activity. This superior performance arose from a unique synergistic interface: CS provided strong electrostatic repulsion, whereas GA offered dense steric hindrance. Combined, these mechanisms could not be achieved by WPI or any single biopolymer. The covalent CS-GA conjugate created a balanced electrostatic-steric barrier that effectively prevented droplet coalescence and lipid oxidation. Thus, the CS-GA composite emulsifier offered a safe, stable, and flavor-friendly strategy for DHA nanoemulsions and provided valuable insights for optimizing lipid delivery systems in functional foods. • A novel DHA nanoemulsion stabilized by sodium caseinate-gum arabic (CS-GA) complexes synthesized via the Maillard reaction was developed. • CS-GA-NE demonstrated superior physical and oxidative stability under freeze-thaw, thermal, salt ion, and long-term storage conditions compared to single-emulsifier systems. • CS-GA-NE significantly inhibited the formation of off-flavor aldehydes and ketones, and maintained the lowest volatile release under both 4°C and 25°C storage.