Texture and Stability of Emulsions: Role of Oscillatory Structural Forces

ABSTRACT

A digitized optical imaging technique was used to obtain the droplet size distribution, texture, and the radial distribution function which determines the inter-droplet interactions in emulsion systems. The effects of sucrose ester and polyglycerin stearic acid ester as emulsifiers on the stability (i.e., creaming) of oil-in-water food emulsions were investigated, ft was observed that as the concentration of the emulsifier was increased, the droplet size decreased, and the emulsion became more monodispersed and the stability increased. This was confirmed by the experimentally determined radial distributions and the structure factors. It was found that the emulsion made with the fatty acid ester was more stable than that with sucrose ester, and was less polydisperse with better texture. A statistical thermodynamic model was applied which accounts for the droplet-droplet interaction forces, i.e., oscillatory structural forces, and the polydispersity effect to predict the creaming velocity of an oil-in-water emulsion. Good agreement was found between the experimentally determined creaming velocity and the model predictions.