Self-Diffusion of Sucrose in Molasses

The self-diffusion coefficient of sucrose in molasses, D mol, has been determined via the pulsed-field-gradient 13 C NMR technique at 25, 50, 80, and 100 °C and a dry matter content of up to 80% w/w. For this purpose 10% sucrose containing 99% 13 C nuclei in the 1 position of the glucose moiety was added. A comparison of D mol with D pure of pure aqueous solutions showed D mol < D pure at the same sucrose water ratio. Viscosities of the molasses, η mol, and pure sucrose η pure solutions were measured over a wide range (1 mPa s to 5000 Pa s) and were shown to obey the empirical formula of Génotelle. The friction coefficient was found to be influenced by the nonsucrose substances of the molasses, the value of the product D mol η mol being greater than that of D pure η pure at the same sucrose/water ratio, with the deviation increasing with decreasing temperature and increasing concentration. The results have significant consequences for the modeling of the technical crystallization process.