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In this research, the rheological behavior of ribbon type Iranian gum tragacanth was investigated at different concentrations (1–5 g/L), temperatures (5–55°C with 10 degree intervals), pH (4, 7, and 10), and rotational speeds (up to 200 rpm). At first, the apparent viscosity of gum tragacanth solutions were measured at 3 concentrations (1, 3, and 5 g/L) during 28 hours in 2 hour intervals. The results showed that the soaking has no significant effect on the apparent viscosity of gum tragacanth solutions. Regarding the influence of the abovementioned factors, our findings revealed that increasing rotational speed or shear rate at low concentrations (1 and 2 g/L) has no effect on the apparent viscosity of the solutions and those samples behaved likewise Newtonian fluids whereas, at higher concentrations (3 to 5 g/L), with increasing the rotational speed the apparent viscosity diminished and the solution consequently showed a Pseudoplastic behavior. In all experiments, alongside increasing the concentration and temperature the apparent viscosity increased and decreased, respectively. In addition, pH had no considerable effect on apparent viscosity in most of our samples. For comparison purposes, using mathematical equations, experimental findings (namely rotational speed) were converted to fundamental parameters (shear rate and shear stress) as well.

Keywords: Rheology, Flow behavior, Gum tragacanth (Katira), Apparent viscosity

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