At the core of xanthan gum lies its polysaccharide chain; its backbone consists of glucose units linked together via β-1,4 glycosidic bonds to form a long, linear chain. The linear structure of this backbone provides a stable scaffold for the entire molecule, enabling it to maintain its intermolecular arrangement and structural integrity within aqueous solutions. It is precisely this stable backbone that allows xanthan gum to exhibit remarkable viscosity and excellent rheological properties, even at low concentrations. Extending from specific glucose units along this backbone, the xanthan molecule features trisaccharide side chains composed of mannose, glucuronic acid, and mannose. The glucuronic acid residues within these side chains bear carboxyl groups (–COOH), which can form salts with metal ions-such as sodium, potassium, or calcium-thereby converting xanthan acid into xanthan gum. These side chains not only enhance the molecule's steric structure and solubility but also endow xanthan gum with non-Newtonian fluid characteristics; this means its solutions exhibit increased fluidity when subjected to stirring or shear forces, yet retain their consistency when left to stand.
The carboxylate groups within xanthan gum are central to its molecular functionality. By forming ionic bonds with metal ions, xanthan gum acquires resistance to acids, bases, and salts, as well as a certain degree of thermal stability. These salt groups bolster the molecule's stability in aqueous environments, enabling it to maintain its colloidal structure under complex conditions while imparting a diverse range of functions, including emulsification, suspension, and thickening. Consequently, xanthan gum serves simultaneously as a polymeric polysaccharide and a functional salt-based material, holding significant value and application across the food, pharmaceutical, cosmetic, and industrial sectors.
