Rheology of solid Gazıantep Pekmez Original Research Article

The rheological behavior of solid pekmez (concentrated grape juice, °Brix=82.1) with different solid contents (72.9, 66.8, 57.2 and 52.1 °Brix) was studied in the temperature range of 10, 20, 30, 40 and 50 °C using a controlled stress rheometer. Solid pekmez was found to exhibit non-Newtonian behavior, however, diluted samples are Newtonian. The effect of temperature on viscosity can be described by means of an Arrhenius equation. Depending on the soluble solid contents, the activation energies for flow of diluted samples vary from 43.85 to 15.93 kJ/mol. The effect of soluble solids on viscosity can be described by an exponential equation. Experimental data were fitted to several models in order to describe the effect of temperature and soluble solid content. The combined effect of temperature and soluble solid content of viscosity was also formulated.