From egg yolk/κ-Carrageenan dispersions to gel systems: Linear viscoelasticity and texture analysis

The effect of pH (3.5–6) and polysaccharide concentration (0–0.5 wt%) on the linear viscoelastic behaviour of egg yolk/κ-Carrageenan (EY/κC) mixtures in aqueous solution was studied by using Small Amplitude Oscillatory Shear (SAOS). Native egg yolk containing 45 wt% solids was used for all the samples. Thermally set EY/κC gels were also studied by SAOS and texture analysis. A variety of linear viscoelastic behaviours depending on κC concentration and pH were exhibited by EY/κC dispersions that may be explained in terms of the contributions of electrostatic attractive interactions and an exclusion volume effect between protein and polysaccharide macromolecules. This last effect seems to be dominant as pH shifts towards the isoelectric point (IEP) of egg yolk proteins, whereas, at pH far from the IEP a certain enhancement in the degree of compatibility, and even some κC autohydrolysis, seems to take place. The results obtained either from rheological or textural characterization of gels were consistent with that balance. In any case, the results obtained suggest that the microstructure of gels is governed by the protein ability to form gels, where hydrophobically driven interactions and subsequent cross linking among protein segments play a dominant role.