Colourants formed during extraction and refining processes, are differently fixed and removed from resins. Guimarăes et al., 1996, using HADP, melanoidins and caramels, laboratory made, observed that these colourants present different behaviours during decolourization and resin (Table).
Decolorization with styrenic and acrylic resins in presence of NaI
Table - Colourants behaviour during decolourization with resins
By these results, it is observed that styrenic resins efficiently remove HADP and melanoidins. Caramels are not efficiently removed by these resins. In resin regeneration with NaCl at 50g/l and 100g/l, melanoidins are practically removed totally. However HADP and caramels are not efficiently removed. This fact can be explained by the apolar nature of one part of these compounds, as it was observed by sucrose chromatography (Bento, 1994). This, will increase the possibility of colourants remain irreversibly fixed to the resin, by the switch between the two fixation mechanisms. By this fact resin capacity will decrease.
These results were confirmed by GPC chromatography with an ELS. In these studies it was observed that compounds of molecular weight between 12kD and 50kD, Group B, on which part of mealnoidins are, were totally removed by resins (Table 9; Figure 35) (Bento and Sá, 1998). By the Table 9, it is observed that Group C compounds practically are maintained after resins. This fact can be explained by the difficulty of removal of HADP, belonging to this group, during regeneration. In next cycles, these compounds can be dislplaced by higher charged colourants. It was observed that this displacement increases with cycle time (Bento and Sá, 1998).
Figure : ELS diagrama of fine liquor (after resins)
Bento L.S.M., 1994, Separation of sugar colourants using sucrose crystals in chromatographic columns,
Proc. of S.I.T. Conf., 17-39; Zuckerindustrie, 120 (1995) nr.2,123-130
Bento L.S.M., S. Sa, 1998, tudy of HMW compounds in sugar liquors from carbonatation and ion-exchange
resins using chromatography with an evaporative light scattering detector, Proc.of S.P.R.I. Conf.,
Guimaraes C., L.S.M. Bento, M. Mota, 1996, A study of sugar colourants through ion exchange and salt
regeneration, I.S.J., 98, 584-587