The application of diffusing-wave spectroscopy to monitor the phase behavior of emulsion-polysaccharide systems

Droplet aggregation is an important cause of instability in emulsions becau se it may, on one hand, lead to an increased creaming rate, resulting in fa st separation of a concentrated emulsion phase (creamed layer). On the othe r hand, it may also lead to the formation of a stabilizing, droplet-based n etwork. Early detection of instability is often difficult due to the high t urbidity and viscosity of more concentrated food emulsions. The applicabili ty of diffusing-wave spectroscopy (DWS) for monitoring droplet aggregation and creaming was studied using a model system consisting of a protein-stabi lized emulsion, to which a soluble polymer ("thickener") was added. This ad dition leads to an increased solvent viscosity and may induce droplet aggre gation. In addition, the redistribution process of emulsion droplets in agg regating concentrated emulsions was directly observed by confocal scanning laser microscopy (CSLM). By DWS the decrease of the droplet mobility caused by the viscosity increase of the continuous phase could be separated from the effect of droplet aggregation. Moreover, a distinction could be made be tween aggregation, leading to increased creaming rates and that leading to the formation of a stabilizing droplet network. The potential of DWS for in situ measurement of the stability of concentrated emulsions is discussed. (C) 2000 Academic Press.