Influence of alginate concentration and molecular weight on functional properties of mayonnaise

The rheological properties of mayonnaise containing alginates from Macrocystis pyrifera as stabilizers were studied using a controlled stress rheometer and a texture analyser penetrometer. Dynamic oscillatory tests of the emulsions were carried out in strain sweep and frequency sweep modes. The rheological parameters used for this study were the storage (G'), loss (G") and complex (G*) moduli and the strain, which determined the limit of the linear viscoelastic region (gamma(c)) The effect of alginate concentration (.0.2, 0.5 and 0.8 g/100 g) and molecular weight (MW: 76, 120 and 154 kDa) on physical properties was examined and the best combination useful to minimize differences between the alginate emulsion and mayonnaise with modified corn starch as commercial reference was identified (0.35 g/100 g and 108 kDa). The storage modulus increased with alginate content and it became independent of the molecular size above a critical value between 76 and 120 kDa. A positive effect of MW on gamma(c) was observed at 0.2 g/100 g alginate and the critical strain decreased with increasing polymer concentration up to 0.5 g/100 g. Results under small-amplitude oscillatory shear tests (linear viscoelastic properties) were interpreted in the context of the weak gel model. Two material parameters were determined to describe the rheological structure of the emulsion: the coordination number (z) and the parameter A (G* at 1 Hz). Mayonnaises with alginate concentrations of 0.5 and 0.8 g/100 g and at all the MW had coordination numbers which were not significantly different from those of the reference sample. The emulsion strength of alginate samples with polymer concentration of 0.5 and 0.8 g/100 g was significantly higher than the control.