Some Physical, Chemical, and Rheological Properties of Sweet Sorghum (Sorghum Bicolor (L) Moench) Pekmez (Molasses)

Abstract

Some physical, chemical properties and the rheological behaviour of the sweet sorghum (Sorghum bicolor L Moench) pekmez (molasses) were determined. The rheological behaviour of the sweet sorghum pekmez (concentrated sorghum juice) with different soluble solid contents (75.1, 72.4, 66.5, and 59.4 °Brix) was determined in the temperature range of 10, 20, 30, 40, and 50°C using a rotational viscometer equipped with spindle 5 at the speed (share rate) of 5, 10, 20, 50, and 100 rpm. An empirical power law model was used to describe the rheological behavior of the sweet sorghum pekmez with correlation coefficients (R²) between 0.922 and 0.986. The sweet sorghum pekmez exhibited a pseudoplastic behavior. An Arrhenius equation was used to describe the effect of temperature on viscosity and E_a value of the sweet sorghum pekmez was calculated as 31 350 J/mol. Depending on the soluble solids contents, the activation energies for flow of diluted samples vary from 52.27 to 24.50 kJmol⁻¹. The effect of °Brix on viscosity can be described by the power-law equation. Experimental data were fitted to power law and exponential model in order to describe the effect of temperature and soluble dry matter content. Density and Electrical conductivity were measured 1.3915 g/cm³ and 13.53 mS/cm, respectively. The color as L, a and b value were measured 19.07, + 4.0, and + 2.18, respectively.

Keywords:

• Sweet sorghum
• Pekmez
• Viscosity
• Power-low model
• Exponential model
• Arrhenius equation