Depletion flocculation effects in egg-based model salad dressing emulsions

The influence of dehydrated egg white (DEW) addition on the droplet aggregation of yolk-based model salad dressing emulsions was studied in an attempt to investigate the role of the egg albumen fraction in the physicochemical changes that take place during the storage of acidic emulsions containing whole egg. Analysis of the adsorbed protein in emulsion by the application of SDS–PAGE provided strong evidence for the almost complete exclusion of the egg albumen from the droplet surfaces by the more flexible yolk lipoproteins. The results on emulsion stability are discussed in terms of possible depletion effects that may arise from the presence of the non-adsorbed egg white proteins in the continuous phase. Observations of emulsions under the light microscope and rheological measurements are presented to support the hypothesis that the extensive droplet–droplet aggregation effects, arising from the presence of unadsorbed albumen proteins, result in emulsion destabilization against creaming.