Study on removal of coloured impurity in soybean oligosaccharides extracted from sweet slurry by adsorption resins Original Research Article

The dark colour of soybean oligosaccharides extract from sweet slurry, a byproduct of soybean sheet production limits its full utilisation in the food industry. Adsorption resins were performed to remove the coloured impurity. The effects of operation parameters on decolourisation efficiency and adsorption isotherm were investigated. The experimental results revealed that more than 70% of the coloured impurity was removed in final products by macroporous resin DM-130 after 24 h contact. Temperature had significant influence on adsorption. The adsorption process and the thermodynamic data indicated that the process was possibly exothermic and spontaneous. The optimum ratio of resin mass/oligosaccharides solution was approximately 0.13 g/ml. The adsorption isotherm agreed with Freundlich model, indicating that the adsorption process was monolayer and heterogeneous. Adsorption kinetics fitted the pseudo-second-order kinetic model. The second step of intra-particle diffusion would be the rate-controlling step.