Encapsulation of β-carotene in calcium alginate hydrogels templated by oil-in-water-in-oil (O/W/O) double emulsions

Multiple emulsions provide a facile route for particle preparation due to their ability to be used as liquid templates. Herein, biocompatible oil-in-water-in-oil (O-1/W/O-2) double emulsions were fabricated using a two-step procedure and applied as templates for preparation of calcium alginate hydrogels with encapsulated beta-carotene. The encapsulation efficiency (EE) of beta-carotene showed a positive correlation to the outer-to-inner droplet size ratio of the O-1/W/O-2 emulsion. The maximum EE, -50 wt%, could be achieved in the freshly prepared O-1/W/O-2 emulsion when using aqueous alginate of 2 wt% as the intermediate phase and beta-carotene loaded R-(+)-limonene of 0.1 wt% as the inner oil phase. Gelation of the alginate phase was induced by addition of a small amount of aqueous CaCl2 into the beta-carotene-loaded O-1/W/O-2 emulsion. The resulting hydrogels in water were characterized by laser diffraction and several microscopy measurements. The hydrogels showed good spherical shape and their average size was a little larger than that of the emulsion droplet templates. This work contributed to the understanding of encapsulation in O-1/W/O-2 emulsion system and provided a novel methodology for encapsulation of carotenoids and other lipophilic bioactives.

Automated summary

Multiple emulsions provide a facile route for particle preparation due to their ability to be used as liquid templates. In this study, O-1/W/O-2 double emulsions were used as templates for preparing calcium alginate hydrogels encapsulating beta-carotene, with encapsulation efficiency showing a positive correlation to the outer-to-inner droplet size ratio. The resulting hydrogels exhibited good spherical shape in water, slightly larger in size compared to the emulsion droplets used as templates.