(352a) Emulsion Texture and Stability: The Role of Surfactant Micellar Interactions

Food beverages such as milk coffee are fat/oil-in-water emulsions containing small amounts of fat (oil), proteins, coffee or tea extracts, sugars, and emulsifiers or stabilizers. Over time, oil droplets, which have lower density than the continuous medium, cream to the top, resulting in a ring formation. Also, very often, oil spreading or the ?oiling-off' phenomenon, which is due to the destabilization of emulsions, is unappealing to consumers. We have investigated these phenomena in a model milk coffee system using the Kossel diffraction technique to evaluate the emulsion texture and energy barrier between droplets. We have used a differential microinterferometric method to examine the role of micellar (emulsifier) interactions and the changes in the stability of the confined film between two droplets. Droplet size distributions in the ring over time were monitored, and the stability of an oil-in-water emulsion was studied. We quantified the surfactant micellar interactions by measuring the second virial coefficient of the micellar solutions. These measurements are being used to gain a mechanistic understanding of both the emulsion shelf-stability and the ring formation of the food beverages.