Ultrasonic studies of the development of flocculation in mixed sodium caseinate and Tween 20 emulsions

Ultrasonic velocity and attenuation measurements were performed for a series of emulsions containing sodium caseinate and Tween 20. The kinetics of creaming were followed in order to establish relationships between depletion flocculant concentration and the onset of creaming. An interesting phenomenon was noticed where attenuation throughout the bulk of the emulsion dropped from very high values to lower ones with time. This was more intense at higher concentrations of Tween 20 (more flocculated emulsions). The lower attenuation values corresponded approximately to the theoretically predicted attenuation spectra for flocculated emulsions. The explanation for the higher attenuation at the beginning of the lifetime of the emulsions seems to be related to the formation of a transient gel spanning throughout the structure, eventually breaking up to produce discretely creaming flocs.