Creaming and flocculation in emulsions containing polysaccharide

The influence of ionic polysaccharides on the stability of hydrocarbon oil-in-water emulsions made using sodium caseinate as emulsifier has been investigated at neutral pH. The four polymers studied were two microbial polysaccharides, xanthan gum and succinoglycan, and two carboxymethylcelluloses of high viscosity (CMC7HOF) and medium viscosity (CMC7MF). In each case, the presence of a small concentration of polymer produced a large increase in creaming, as indicated by the rate of serum separation observed visually. Increasing the polymer concentration led to improved creaming stability due to the rheological effects of the polymer in the continuous phase. The relative stabilizing abilities of the polysaccharides lie in the order: succinoglycan > xanthan gum ≫ CMC7HOF > CMC7MF. Complementary turbidity fluctuation measurements provide evidence for emulsion droplet flocculation in the presence of all four anionic polysaccharides. The effects of ionic strength on creaming and flocculation were investigated: the results confirm the general destabilizing effect of polysaccharides on food emulsibns at low concentrations. The extent to which the phenomenon may be generally ascribed to depletion flocculation, as opposed to some kind of bridging flocculation, is discussed in the light of other recent experimental observations.