Enhancing 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 its physicochemical stability and digestibility of the 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. Zeta-potential, particle size, size distribution, physical stability, microstructure, DHA oxidation and free fatty acids release rate in a simulated gastrointestinal tract (GIT) model were determined. Dynamic light scattering and confocal laser scanning microscopy 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-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 its 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 offer useful information for the stabilization of functional food components and rational design of nutraceutical delivery systems.