Study of coloured components formed in sugar beet processing

The main characteristics of the most troublesome colourants formed throughout sugar beet manufacture are summarised. A review of the reaction mechanisms, structures and factors affecting their formation is presented to enhance understanding of the nature of coloured impurities and to propose effective measures for controlling their formation through the process. The main colourants formed in sugar beet processing were synthesised, analysed by gel permeation chromatography (GPC) and characterised by their molecular weights and UV–Vis spectra. The GPC analysis of a sugar beet thin juice showed the presence of coloured compounds with molecular weights ranging from 0.4 to >100 kDa. Spectral analysis confirmed the presence of melanoidins and alkaline degradation products of hexoses in the juice. There is a substantial increase in colour after the evaporation step. Therefore, the coloured impurities of thin juices have to be removed before subsequent stages to produce white sugar of high quality.