Exploiting multiple phase separation to stabilize water in water emulsions and form stable microcapsules

Water in water (W/W) emulsions are formed by mixing aqueous solutions of incompatible polymers. It is possible to add a third polymer solution that forms at the right conditions a phase that completely covers the dispersed droplets as a thin layer. Our hypothesis is that by gelling the third phase, W/W emulsions can be stabilized and that microcapsules can be formed that are stable against dilution.

W/W emulsions were formed by mixing aqueous solutions of poly(ethylene oxide) (PEO) and dextran. Gelatin was added to form the third phase, gelation of which was induced by cooling. The morphology was observed by microscopy, and the rheological properties were investigated.

The compatibility of gelatin and PEO can be fine-tuned by the pH such that a continuous layer of the gelatin phase forms around the droplets of the dextran phase, with a thickness that can be varied. After cooling, the gelatin layer forms a gel and provides stabilization against coalescence. The gelatin microcapsule was found to be stable to dilution. The generality of the method was demonstrated by applying it to another, fully food-grade, W/W emulsion formed by mixing amylopectin and xyloglucan.