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 (O1/W/O2) double emulsions were fabricated using a two-step procedure and applied as templates for preparation of calcium alginate hydrogels with encapsulated β-carotene. The encapsulation efficiency (EE) of β-carotene showed a positive correlation to the outer-to-inner droplet size ratio of the O1/W/O2 emulsion. The maximum EE, ∼50 wt%, could be achieved in the freshly prepared O1/W/O2 emulsion when using aqueous alginate of 2 wt% as the intermediate phase and β-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 β-carotene-loaded O1/W/O2 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 O1/W/O2 emulsion system and provided a novel methodology for encapsulation of carotenoids and other lipophilic bioactives.