Sensitive Detection of the Separation of Emulsion by High-Frequency Spectroscopy

Abstract

The stability of an emulsion could be monitored by high-frequency spectroscopy. The results for an o/w-type emulsion showed that the frequency shifts with the passage of time were affected by the speed of stirring and/or by the temperature of storage. The amount of the frequency shifts was in good agreement with the average particle size observed by an optical microscope. This means that high-frequency spectroscopy can detect the progress of a creaming effect due to separation of the emulsion. A similar series of experiments was conducted for an w/o-type emulsion and a commercial product of emulsion, leading to similar observation results. These results show that high-frequency spectroscopy is effective for a rapid evaluation of the stability of w/o- and o/w-type emulsions as well as a multi-ingredient emulsion.