Enhancing the physicochemical stability and digestibility of DHA emulsions by encapsulation of DHA droplets in caseinate/alginate honeycomb-shaped microparticles

Docosahexaenoic acid (DHA) was encapsulated in caseinate/alginate microparticles by adjusting the pH based on the electrostatic complexation, in order to improve the physicochemical stability and digestibility of single caseinate-stabilized DHA emulsions. In this study, relatively stable honeycomb-shaped DHA microparticles were formed by electrostatic complexation between positively charged caseinate-coated DHA droplets, caseinate and negatively charged alginate at pH 4.5. The zeta-potential, particle size, size distribution, physical stability, microstructure, DHA oxidation and free fatty acids (FFA) release rate in a simulated gastrointestinal tract (GIT) model were determined. Dynamic light scattering (DLS) and confocal laser scanning microscopy (CLSM) measurements indicated that DHA microparticles had a particle size (1521.00 ± 39.15 nm) significantly larger than that of caseinate-stabilized DHA emulsions (243.23 ± 4.51 nm). The microparticles were much more stable near the isoelectric point (pI) of the adsorbed proteins compared with the single emulsions according to the original transmissions of LUMiSizer. The cryo-scanning electron microscopy (Cryo-SEM) images also showed that the microparticles formed a specific honeycomb-shaped network structure with more uniform distribution and without aggregation. The incorporation of DHA droplets into caseinate/alginate microparticles significantly ameliorated their chemical stability. GIT studies showed that the digestion of DHA microparticles was enhanced which was due to more open loose structures compared with the large-scale close-knit aggregation of DHA emulsion droplets. This study may provide useful information for the stabilization of functional food components and rational design of nutraceutical delivery systems. DHA was encapsulated in caseinate/alginate microparticles by adjusting the pH based on the electrostatic complexation, in order to improve the physicochemical stability and digestibility of single caseinate-stabilized DHA emulsions.