Influence of xanthan gum on physical characteristics of sodium caseinate solutions and emulsions

Influence of xanthan gum (XG) on the properties of the solution containing 3.0 wt% sodium caseinate (CN) was estimated firstly by zeta potential, hydrodynamic diameter (DH) and interfacial tension. CN–XG mixture solutions showed larger DH and lower negative zeta potential at higher XG concentration, indicating that molecule interactions may take place in solution. The surface activity of CN was improved with addition of XG at 0.01 wt%, while it weakened to a great extent at 0.04 wt% XG. Then, the influence of XG on the concentrated (36 wt%) emulsion, stabilized with 3.0 wt% CN was assessed by droplet diameter and dispersion characteristics, apparent viscosity, surface protein concentration and microstructure. Results showed that emulsion without XG, characterized by the lowest surface protein concentration and apparent viscosity, showed no sign of flocculation but coarse oil droplets. Increase in XG concentration led to an increase followed by a decrease in d4,3, uniformity values and partial coalescence of fat, while inversely, surface protein concentration decreased firstly and then increased. CLSM images showed extensive enrichment region of XG and depletion flocculation at XG concentration above 0.01 wt%.

Graphical abstractConfocal micrographs of whipping cream (36 wt% anhydrous milk fat, 3 wt% CN, and pH 6.8) with selected XG concentrations. Scale bar represents 50 μm. Particle size distribution of emulsions determined by light scattering (Mastersizer 2000) is superimposed on the micrographs, with horizontal scale numbers indicate particle size (μm) and vertical scale numbers indicate volume (%).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► 0.01% XG raised the surface activity 1 of CN solution while other contents 2 weakened. ► The presence of XG increased absolute zeta potential and DH of XG–CN mixtures. ► CN-stabilized emulsions in the presence of XG all showed depletion flocculation. ► Emulsion with 0.01% XG was the most stable one while 0.04% was the worst one.