Sucrose crystallize in monoclinic crystals, with dimensions between some decimal of millimeters up to some centimeters, in commercial sugars. In sugar refining, this operation is done under vacuum in order to have moderate temperatures (65ºC to 75ºC) with a convenient crystal grow velocity. Crystallization is done in single effect evaporators (vacuum pans) where sugar solutions are concentrated from about 78º Brix till a supersaturation between 1,15 e 1,25. In this zone spontaneous formation of crystals does not occurs and the existing ones does not dissolve and will grow. In order to form crystals in concentrated liquor and to start crystallization, a suspension of powder sugar in ethanol or iso-propanol is added to the liquor (Seeding). These added crystals will grow, during the crystallization, until the desired dimension. Another process consist in fedding the pan with a seed magma. This magma can be prepared throgh a crystallization at low temperature. This process will produce crystals of high quality.
In the final of crystallization operation, massecuite is concentrated in the vacuum pans, before be discharged into the storage receivers (mixers or crystallizers).
Chen J.P.C. (1993) “The crystallization of sugar”, in Cane Sugar Handbook, Ed.