WATER-SUCROSE INTERACTIONS, QUALITY OF CRYSTALS AND THE STORAGE STABILITY OF WHITE SUGAR

摘要

Caking of white sugar can be considered as a spontaneous agglomeration phenomenon which occurs under certain conditions of quality of crystals (especially large C.V., broken crystals, presence of amorphous and fine particles) and characteristics of surrounding air (temperature, relative humidity). To account for the interactions between water and sucrose in the thin layer of syrup surrounding the sugar crystal, water vapour sorption isotherms are obtained at different temperatures and the water content at the surface and inside the crystals determined using the Karl Fischer titration method. To characterize the quality of crystals and the defects engendered during the manipulation of dry sugar in dryers, coolers, elevators and sieves, image analysis was used applying LUCIA software to the images of crystals obtained with Nikon binocular and camera. A relation exists between the quality of sugar crystals and their flowability in silos determined with a Jenike shear cell. To thoroughly understand the mechanism of caking, there is a need of approaching both the macroscopic visual image of the crystals and the microscopic molecular interactions between water and sucrose.