Evaluation of rheological properties of date syrup

Abstract

Rheological behavior of date syrup is an important factor affecting the efficiency of sugar production and refining processes such as boiling, crystallization, separation and pumping. A rotational viscometer was used to characterize the flow behavior of date syrup solution at four different temperatures (20°C, 40°C, 60°C and 80°C) and four concentrations (17, 24, 31 and 39°Brix). The samples were subjected to a programmed shear rate increasing from 10 to 100s−1 in 2min, held constant at 100s−1 for 10min and linearly decreasing to 10 during 2min. The power law model was fitted to shear stress vs. shear rate data to obtain the consistency coefficient (m) and the flow behavior index (n). Both m and n were sensitive to changes in temperature and concentration. The apparent viscosity increases with increasing concentration of date syrup and a decrease in temperature.