Comparative analysis of dextran-induced sucrose crystal modifications

The analysis of sucrose crystal size and shape modifications induced by the presence of dextran was key to this study. Therefore, evaporative crystallisation experiments using synthetic thick sucrose juices containing various contents of high molecular mass dextran (T2000) were performed. HPLC analysis of the dissolved sucrose crystals revealed that T2000 dextran gets incorporated into the sucrose crystal, indicating that dextran-related crystal size and shape modifications occur. For analysing the sucrose crystal size and shape distribution, static image analysis was implemented and compared to common sieve analysis as well as dynamic image analysis (Camsizer). All methods consistently indicate an increase of crystals with lower minimum and especially lower maximum feret diameters due to the presence of T2000 dextran. For the sucrose crystal shape analysis, average values and relative frequency distributions were evaluated. For more detail, the shape data were further processed using a crystal size-dependent evaluation. Thereby, it was found that cube-shaped crystals, elongated needle-shaped crystals and agglomerates can be related to the presence of dextran. The data suggest that the occurrence of the three dextran-related shapes depend on the dextran content present and also relate to certain sucrose crystal sizes. This way, cube-shaped crystals could be related to small-sized crystals, predominantly occurring at lower dextran contents. Agglomeration and distinct elongation were found to be related to mid- and especially large-sized crystals. The latter two, especially distinct elongation, seem to increasingly occur when higher dextran contents were present.