Conformation and shear stability of xanthan gum in solution

Xanthan gum, the extracellular polysacchuride produced by the microorganism Xanthomonas campestris has unique rheological properties and as a result found many industrial uses. The primary structure o xanthan consists of a cellulose backbone substituted on alternate residues with charged trisaccharide side chains. The polymer undergoes an ordered ⇄ disordered conformation transformation, Very recently determinations of the secondary and tertiary structures have shown that the ordered conformation is helical. The two conformations have different solution properties. Rheological evidence indicates that xanthan conformation is critically dependent on the presence or absence of‐salt. In this work we show that the polymer shear degrades to a larger extent in the disordered conformation than in the ordered conformation. That is, the ordered conformation is more shear stable.