Tapioca starch-galactomannan systems: Comparative studies of rheological and textural properties.

Rheological properties of tapioca starch-galactomannan mixtures at different concentrations (0, 0.3, 0.6 and 1.0%, w/w) of guar gum, tara gum and locust bean gum were investigated in visco-analysis, steady and dynamic shear and textural analysis. Galactomannans may influence the pasting temperature and other pasting parameters, the viscosity and pseudoplasticity of the blend systems increased as time-dependence and thixotropy decreased. This can be explained by the phase separation of systems where the galactomannans were placed in the continuous phase and the volume fraction of starch granules increased its concentration in the disperse phase. The addition of guar gum and tara gum could accelerate the formation of new structures and increase the degree of structural recovery until a 50% more than the starch gel pastes. The apparent viscosity (ηa) and dynamic moduli (G' and G″) of the mixed pastes increased with the addition of galactomannans. Changes in textural properties were significant. The gel hardness, gel strength and adhesiveness of gel pastes were higher in the starch-tara gum and starch-locust bean gum systems than in the starch-guar gum system in gum concentrations values of 0.3 and 0.6% w/w. Overall, addition of galactomannans affected the rheological and textural properties of tapioca starch.