Rheological properties and stability of model salad dressing emulsions prepared with a dry-heated soybean protein isolate-dextran mixture

The rheological characteristics of model salad dressing emulsions, incorporating a dry-heated soybean protein isolate (SPI)-dextran mixture as emulsifier, were investigated by applying dynamic rheometry tests in an attempt to probe the emulsion structure and to elucidate the mechanism of their stability against creaming. Both the viscoelastic properties and the creaming behaviour of the dressings were greatly influenced by the extent of protein-dextran conjugation and also by xanthan gum addition. The results are discussed in terms of emulsion droplet interactions which, depending on the extent of glyco-conjugation, may be dominated by depletion or 'bridging' flocculation effects and, thereby, influence the droplet network structure collapse during ageing.