Preparation of a stable gel-in-crystallized oil-in-gel type structured W1/O/W2 double emulsions: effect of internal aqueous phase gelation on the system stability

Abstract

This work reported a strategy to improve the storage stability of W1/O/W2 double emulsions with the combination of the gelled internal aqueous phase, crystallized lipid phase, and gelled external aqueous phase. The composite of κ-carrageenan and locust bean gum (κ-C/LBG) was a suitable gelling agent of the internal aqueous phase. Crystallized oils were formed by the addition of solid lipid (glycerol monostearate, GMS) into the oil phase. The double emulsions fortified by gelled inner droplets were filled in Ca-alginate hydrogel beads. The results demonstrated that GMS formed crystalline layers at the oil-water interface, and its concentration significantly affected the morphology and droplet size of double emulsions. The total polymer concentration of κ-C/LBG had an effect on the droplet size and entrapment efficiency of double emulsions. Furthermore, thermal stability study (2–21 days) and long-term storage stability study (24 weeks) showed that the gelation of the internal aqueous phase with a low concentration of 0.5 wt% κ-C/LBG appreciable increased the retention efficiency of the encapsulated double emulsions compared with the system of the non-gelled internal aqueous phase, which might provide a useful method to promote the production of double emulsions.