The effect of shear on these emulsions was investigated. By recombining variable amounts of these phases, thereby varying only their volume fractions, we were able to prepare stable emulsions with constituents having constant compositions. The individual phases were then characterized through their viscoelastic and flow behaviors. For the rheological investigations, starting with an initial composition of the system, we separated the two phases by centrifugation. We first characterized the biopolymers and determined the phase diagram at room temperature that we interpreted within the framework of the Edmond and Ogston model. We investigated a ternary system composed by two biopolymers, a protein (caseinate) and a polysaccharide (alginate) in aqueous solution and established an analogy between these phase separated solutions and immiscible blends of polymers. Provided the time stability of the emulsion is long enough and the size of the droplets does not exceed a few tens of microns, the emulsion can be characterized by conventional rheological methods as an effective medium, both in the linear regime (viscoelasticity) and under flow. With time, the smaller droplets tend to merge into larger ones and eventually sediment. Both phases contain two types of polymers and solvent in variable amounts. Partially miscible polymers in solution do not separate into two macroscopic phases in general they behave as viscoelastic fluids containing droplets of the minority phase dispersed into a continuous majority phase (emulsion type systems).

Water in water emulsion