Glycerol‐Regulated Water Content in DHA Algal Oil Emulsions: Effects on Emulsion Stability and Oxidative Stability of DHA Algal Oil

This study constructed DHA algae oil emulsions using sodium caseinate (NaCS) as an emulsifier and by controlling the mass fraction of glycerol in the aqueous phase (0-90 wt%). The differences of physicochemical properties, oxidative stability, and bioaccessibility were systematically investigated. The findings indicated that the incorporation of glycerol significantly enhanced the emulsion performance. The emulsion with high glycerol content (90 wt%) exhibited the smallest droplet size (185.6 ± 4.05 nm), the highest apparent viscosity and shear modulus, demonstrating weak gel characteristics, and maintained excellent stability within the pH range of 3-8 and under centrifugal conditions. By inhibiting the dissolved oxygen in the aqueous phase and delaying oxygen diffusion, the glycerol emulsion significantly slowed down the oxidation process of DHA algae oil, with lower primary oxidation products (POV) and secondary oxidation products (TBARS) compared to the conventional emulsion (0 wt% glycerol). Additionally, it inhibited the oxidation of tryptophan and the formation of Schiff bases in NaCS, effectively suppressing protein oxidation. In vitro simulated digestion experiments showed that the DHA bioaccessibility of all emulsions was above 85%, which was three times higher than that of pure algae oil (27.8%), and the glycerol content had no significant effect on it. This study confirms that the low-water glycerol-NaCS emulsion system can synergistically enhance the oxidative stability and bioavailability of DHA algae oil, providing a new strategy for developing long-lasting and stable functional lipid delivery systems.