Cascade analysis of mixed gels of xanthan and locust bean gum

The gel properties of xanthan (XG)–locust bean gum (LBG) mixtures were investigated. The concentration and temperature dependence of gel modulus, as well as the composition dependence of critical gelling concentration, were analyzed using a cascade model. The number of cross-linking sites per molecule for XG and LBG, fXG and fLBG, is determined by fitting experimental data to the model. The values of fXG = 100 and fLBG = 1000, obtained from the concentration dependence of gel modulus, imply that a cross-link is formed in every 10 repeating units along the XG backbone and the cross-linking site in LBG is composed of segments with more than three consecutive unsubstituted mannose residues. An anomalously high value of fXG is obtained from the temperature dependence of gel modulus, probably due to the existence of a secondary mechanism during the rheological meltdown process. The cascade analysis of the composition dependence of critical gelling concentration results in values of fXG = 30 and fLBG = 5. These values reflect that the critical gelling concentration measurement probes only the cross-links formed via long segments of XG and LBG.