Stability and Rheology of Dispersions Containing Polysaccharide, Oleic Acid and Whey Protein Isolate

The effects of whey protein isolate (WPI; 2, 4% [w/w]), xanthan gum (XG; 0.5, 1% [w/w]) and oleic acid phase volume fraction (5, 10% [v/v]) on the stability and rheological properties were investigated. The droplet size distribution, creaming index and rheological properties of dispersions were measured. Results showed that both G′ and G″ increased with xanthan and oil phase volume fraction. However, the viscoelastic behavior was mainly governed by the XG content. The shear‐thinning behavior of both aqueous dispersions (continuous phases) and emulsions was successfully modeled with power law and Cross models; the power law model was found to better describe the flow behavior of dispersions. Droplet size distribution was measured by light scattering; microscopic observations revealed a flocculated system. An increase in XG, WPI concentration and oil volume fraction resulted in a decrease in creaming index of emulsions, with XG concentration having the dominant effect. PRACTICAL APPLICATIONS Emulsions and dispersions are of great interest in many fields, including most food and cosmetic industries. This study shows the effect of XG and WPI concentrations and oil phase volume fraction on the stability and rheological properties of dispersions. The results are useful in developing a relationship between emulsion properties and emulsion stability. WPI has the potential to be used for the manufacturing of stable dispersions without any significant effect on rheological properties.