New insights into the study of the destabilization of oil-in-water emulsions with dextran sulfate provided by the use of light scattering methods
Résumé
Emulsions are non-thermodynamically-stable systems. Being able to characterize their evolution upon time without disturbing them would be of great interest. Mechanisms of destabilization: depletion and bridging flocculation were reproduced by using dextran sulfate respectively with Tween 20 and whey-protein-stabilized oil-in-water emulsions. Two light scattering methods were combined: Multiple Light Scattering, MLS, specially adapted to characterize turbid systems (Turbiscan (R)) and Multi-Speckle Diffusing Wave Spectroscopy, MS-DWS (Rheolaser (TM)). The Tween 20-stabilized emulsion showed a very stable-versus-time elasticity index (El) measured by MS-DWS up to 24 h. On the contrary, the whey-protein-stabilized emulsions showed a large variation of El that decreased continuously during 10 h and dropped to zero suddenly. On the basis of the physico-chemical interaction knowledge and the MLS profile evolution versus time, a variation of the destabilization kinetics depending on the droplet network stabilization but also on the interactions between droplets and the surface of the recipient was proposed. It was confirmed by the modification of the destabilization kinetics when changing the solid surface tension of the recipient.