Rheological characterization of tahin/pekmez (sesame paste/concentrated grape juice) blends

Rheological properties of tahin/pekmez blends were determined at different tahin concentrations (20-32%) and temperatures (35-65 °C) by using a concentric cylinder rotational viscometer. Tahin/pekmez blends were found to exhibit non-Newtonian, shear thinning behavior at all temperatures and tahin concentrations. Apparent viscosity versus shear rate data was successfully fitted to the power-law model. The flow behavior index, n varied in the range of 0.7-0.85. The consistency coefficient, K, was in the range of 282-2547 mPa sn. Both parameters were significantly affected by temperature. The effect of temperature on n did not follow a descriptive trend while the relation between temperature and K was described by an Arrhenius-type equation. Activation energies appeared in the range of 13376-28592 J/mol with increasing concentration. The effect of concentration was significant for only K and it was described by exponential and power functions. A mathematical expression to relate apparent viscosity to temperature, tahin concentration and shear rate was proposed.