Polysaccharide decolorization: Methods, principles of action, structural and functional characterization, and limitations of current research

The presence of pigments is one of the main factors complicating further study of the structural characterization and biological activity of polysaccharides. Polysaccharide decolorization is an important aspect of polysaccharide impurity removal. However, research on polysaccharide decolorization has not yet been systematically summarized. This review begins by exploring polysaccharide sources and describes the measurement indexes of polysaccharide decolorization. This study focuses on elucidating the principles and main factors influencing decolorization methods. The advantages and disadvantages of decolorization methods were compared, and the importance of desorption studies for decolorization agent selection was emphasized. The structures and functions of polysaccharides before and after decolorization were characterized. The limitations of polysaccharide decolorization have also been discussed. Currently, polysaccharide decolorization research mainly focuses on plant polysaccharides, and polysaccharide pigments originate from the self-carrying and extraction processes. The measurement indices for the decolorization effect were decolorization ratio, polysaccharide recovery ratio, deproteinization ratio, and comprehensive evaluation index. Resin adsorption is the most widely used method for polysaccharide decolorization. Structural characterization was performed to determine whether the polysaccharide structure was destroyed before or after decolorization. The functional activities of polysaccharides before and after decolorization have not been studied sufficiently; therefore, it is difficult to fully reveal the structure-activity relationship. In general, this review contributes to a full understanding of the selection or development of polysaccharide decolorization methods, reveals the limitations of current research, and promotes an in-depth study of polysaccharide decolorization.