Interactions between milk proteins and gellan gum in acidified gels

The mechanical properties, microstructure and water holding capacity of systems formed from whey protein concentrate (0-3% WPC w/w), sodium caseinate (0-2% w/w), and gellan gum (0.1-0.3% w/w) in the coil or helix conformational state (Coil/Helix), were investigated. This polymer combination resulted in bi-polymeric or tri-polymeric systems, which were slowly acidified to pH 4.0 by the addition of GDL in order to favor electrostatic protein-polysaccharide interactions. The properties of the tri-polymeric systems differed considerably from the bi-polymeric ones. At high polymer concentrations the WPC-gellan samples showed incompatibility and microphase separation, which resulted in weaker and less deformable gels. However, in systems with coil gellan the incompatibility was less intense, which was attributed to the formation of electrostatic complexes between the protein and the polysaccharide during the mixing process. In caseinate-gellan systems, complex formation was observed and an increase in the gel mechanical properties as the caseinate concentration rose, although the water holding capacity decreased at higher gellan concentrations. The caseinate-gellan coacervate was not visualized in the tri-polymeric systems and the incompatibility between the biopolymers was intensified, although the mechanical properties were considerably higher than in the bi-polymeric gels. (C) 2009 Elsevier Ltd. All rights reserved.