Eur. Phys. J. E 5, 183-188

Probing particle-particle interactions in flocculated oil-in-water emulsions using ultrasonic attenuation spectrometry

N. Herrmann¹, Y. Hemar¹, P. Lemaréchal² and D.J. McClements<sup>3

1</sup>  Food Technology Research Center, Massey University, Palmerston North, 0800 Massey, New Zealand
²  Laboratoire de Dynamique des Fluides Complexes, Université Louis Pasteur, 4 rue Blaise Pascal, 67070 Strasbourg Cedex, France
³  Biopolymers and Colloids Research Laboratory, Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA

nherrmann@malvern.co.uk

(Received 17 July 2000)

Abstract
The flocculation of silicone oil-in-water emulsions ( ) containing quasi-monodisperse droplets was studied by ultrasound. The ultrasonic attenuation spectra of emulsions with different particle sizes (200-1600 nm) were measured between 0.5 and 10 MHz using an interferometer. Flocculation was induced by adding excess sodium dodecyl sulphate micelles to the emulsions to increase the attractive forces between the droplets. Droplet flocculation decreased the ultrasonic attenuation at low frequencies because of overlap of the thermal waves caused by the close proximity of the droplets within the flocs. A mean-field model which takes into account this effect was used to determine the droplet volume fraction within the flocs and thus to estimate the distance between the droplets.

PACS
43.35.Bf - Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions and emulsions.
82.70.Kj - Emulsions and suspensions.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001