Rheology of water-in-water emulsions: Caseinate-pectin and caseinate-alginate systems

Conventional models developed for oil-water emulsions do not fit viscosity of caseinate-pectin and caseinate-alginate water-in-water emulsions, which is always lower than predicted, except for high viscosities of disperse phase. These models do not consider strong deformations, prevented by the high interfacial tension of oil-water interphases. The ultra-low interfacial tension of water-in-water emulsions facilitates the creation of interphase and very elongated droplets. Capron model considers interfacial tension, fitting results when the dispersed phase is the most viscous, but, for other cases, lower experimental values are obtained related to the shear-induced stratification. Even values below the stratification model are observed for some samples, related to the influence of the interphase in the viscosity of the emulsion. A model that takes into account the presence of a relatively thick interphase poor in both polymers is proposed. Intermediate structures between highly elongated and stratified fluids, with influence of interphase viscosity could explain results.