Dextran-induced depletion flocculation in oil-in-water emulsions in the presence of sucrose

The phase behaviour and mechanical properties of 10 wt% oil-in-water emulsions, stabilised by beta-lactoglobutin (beta-1g) and flocculated by the polysaccharide dextran were studied as a function of sucrose concentration. The sucrose concentration affected neither the polysaccharide concentration above which depletion flocculation occurred, nor the elastic modulus and maximum linear strain of the emulsion gels formed. Furthermore, only a minor change in size of dextran molecules was measured over the range of sucrose concentrations studied. From this we deduce that the depletion potential between the oil droplets was not significantly affected by addition of sucrose. However, the sucrose concentration did affect the rate of macroscopic phase separation, which could be attributed to a larger viscosity and density of the aqueous phase. Thus, in unheated systems sucrose has a kinetic effect on serum separation in depletion-flocculated emulsions but no significant effect on droplet-droplet interactions. (C) 2004 Elsevier Ltd. All rights reserved.