The influence of the linear growth velocity on the properties of sucrose crystals produced from mixed syrups

The systematic study presented addresses the need to understand the co-crystallization of beet and cane material better. This is important because of the sugar market liberalization in 2017. Here the effect of crystal growth velocity on final sugar quality is investigated. Comparing three different thermal setups, studying different cane and beet mixtures color inclusion into sucrose crystals was analyzed. Within one thermal setup supersaturation was practically constant. Almost exclusively the time necessary to complete the crystallization at 50% solids level changed. Particle size and distribution remained unchanged. Hence, only the growth velocity varied. Growth rate appears to influence color inclusion less than mixing of beet and cane syrups. In cane syrups the relative color inclusion is the highest and most sensitive to growth velocities. Admixing only 33% of beet syrup, already changes this pattern dramatically and the color transfer factor is more than halved. This effect of beet material is most prominent for the mechanism liquid inclusion but also significant for co-crystallization of colorants. This observation is possibly due to the different nature of the colorants originating from beet and cane. The findings provide a framework to optimize the space-time yield under consideration of highest sugar quality to manufacturers. Practical applicationsCo-production of beet and cane is a promising opportunity to increase competitiveness by increasing utilization of equipment in the seasonal sugar industry. To do so reliably, quality parameters have to be met. The main problem to be solved is the control of white sugar color. Since cane and sugar beet deliver different coloring minor components, their interaction and respective inclusion mechanisms need to be understood. The work presented is part of a comprehensive study to elucidate this area of sugar processing that has not been studied yet. Next to the findings on inclusion characteristic and relative contribution of different mechanisms, the conclusions can directly be transferred into practice. The data gathered give a clear guidance to producers that higher inclusion levels of colored material, than current conservative practice dictates, can be tolerated due to the mutual suppression mechanism found.