Rheology of xanthan/sucrose mixtures at ultrasonic frequencies

Shear ultrasonic reflectance and oscillatory viscometry were used to measure the dynamic viscosity of xanthan (0% and 0.5%) and sucrose (74-78 wt.%) solutions and their mixtures over a range of temperatures (5-20°C). For the sucrose-containing samples, there was good correlation (r² > 0.97) between the two methods, but poor numeric agreement. On the other hand, the sucrose-free xanthan solutions were indistinguishable from water by the ultrasonic methods. The numeric deviation was attributed to the sucrose glass relaxation and is modeled according to the Maxwell model. Xanthan gum retarded the mobility of sucrose and increased its relaxation time approximately tenfold.