Water-in-water-in-water emulsions formed by cooling mixtures of guar, amylopectin and gelatin

Water-in-water emulsions were formed by mixing aqueous solutions of the neutral polysaccharides guar and amylopectin. The effect of adding gelatin B on emulsions, both of a dispersed guar rich phase in a continuous amylopectin phase and the inverse, were investigated using confocal scanning laser microscopy as a function of the gelatin concentration between 0.25 and 1.5 wt% and the pH between pH 4 and pH 6. Gelatin was found to phase separate upon cooling below about 25 °C in a narrow pH range around pH 5 both in the pure guar phase and in the pure amylopectin phase forming distinct spherical domains. The phase diagram was established as a function of the gelatin concentration and the pH. In the emulsions, the gelatin phase separated first at the interface between the two phases forming a continuous layer at the droplet surface. In some conditions the layer persisted, but in others it broke up into distinct domains. Excess gelatin phase separated in the bulk amylopectin phase, particularly when it was the continuous phase. The gelatin redispersed into the bulk phases when the emulsions were heated to 30 °C.