Rheology and phase behavior of aggregating emulsions related to droplet-droplet interactions

CLAUDIO L. A. BERLI

Costa Verde, Rio de Janeiro, Brasil

Congreso; EMPROMER 2005; 2005

In recent years, significant progress has been made in understanding the theoretical connection between interparticle forces, phase behavior and rheology of colloidal dispersions. The subject is currently discussed in the literature, mainly motivated by the wide technological applications of colloids. In particular, the possibility of relating the flow behavior of emulsions to the interaction between droplets is of interest in the food industry, where the physical properties of products are generally controlled by varying, empirically, inter-droplet forces by additives. In this sense, oil-in-water emulsions prepared with sodium caseinate as emulsifier constitute a model system to study the effects of these interactions. The excess of protein in the aqueous phase yields reversible droplet aggregation by the mechanism of depletion. At a given protein concentration, the gelation threshold is reached and the system becomes solid-like. Thus both phase and flow behavior can be controlled by changing the strength of the inter-droplet attraction. The physicochemical characterization and rheological modeling of these emulsions were described in previous papers. In the present work, the subject is briefly reviewed and further considerations on the relationship between droplet-droplet interaction, gel transition and rheology are given. In fact, from the knowledge of the interaction potential, the critical droplet volume fraction for gelation can be related to the magnitude of inter-droplet forces, and then phase diagrams are derived. In addition, the aggregate compactness is analyzed as a function of the characteristics of the interaction potential. This understanding offers new perspectives in the study of complex food systems.