The flow behavior, thixotropy and dynamical viscoelasticity of fenugreek gum

To discover the potential functionalities of fenugreek gum (FG) in food applications and pharmaceutical industry, steady-shear flow, thixotropy and dynamical viscoelasticity tests were systemically carried out under a range of FG concentration (0.05-2.0%, w/v) and temperature (0-80 degrees C). The results showed that FG aqueous solutions exhibited Newtonian plateaus followed by shear-thinning regions which were found to be well correlated to the Carreau model. It was also found that the pseudoplastic behaviors of the FG aqueous solutions exhibited a concentration dependence. When the concentration of FG was above 1%, the system exhibited a gel-like behavior. Dynamical viscoelastic properties also showed a solid, elastic-like viscoelastic behavior. While solution with FG concentration of 0.05% exhibited a transition from a fluid-like to gel-like structure. The variation of the thixotropic index alpha as a function of FG concentration showed a stronger thixotropic behavior as the polymer concentration increased, which indicated a typical elastic behavior of FG solutions with high concentration. Multiwave temperature ramp test for 1.0% (w/v) FG aqueous solution showed that the solid-like behavior had a strong dependence on frequency rather than temperature, which was consistent with the results of oscillatory frequency sweep test. These results could provide a useful indicator for the applications of FG in food industry and other fields. (C) 2015 Elsevier Ltd. All rights reserved.