Viscous synergism in carrageenans (κ and λ) and locust bean gum mixtures:: Influence of adding sodium carboxymethylcellulose

Synergistic interactions between locust bean gum (LBG) and two types of carrageenans (kappa and lambda) are studied. Viscous synergism index, I-v, as a function of concentration ratio, z = C'(LBG)/c'(car), and shear rate were obtained for every mixture. In both binary systems the values of this index decrease with increasing shear rate. For the LBG + kappa mixtures, I-v presented a maximum at a concentration ratio z congruent to 60/40, which would be considered the optimum proportion of gums in the mixture. However, for the LBG + lambda system, I-v increased with z in the whole interval considered, i.e., the highest synergism corresponded to the lowest proportion of lambda carrageenan. The addition of sodium carboxymethylcellulose (NaCMC) to the binary systems modified the above results. For LBG + kappa + NaCMC mixtures, the maximum I-v values were similar to those corresponding to LBG + kappa system, but the concentration ratio at which these maxima are produced shifted to a lesser proportion of locust bean gum ( = 40/60). Moreover, the presence of NaCMC in the other ternary system totally eliminated the possible interaction between LBG and lambda-carrageenan.