INFLUENCE OF THE ACETYL SUBSTITUENT ON THE INTERACTION OF XANTHAN WITH PLANT POLYSACCHARIDES .2. XANTHAN-GUAR GUM SYSTEMS

A range of xanthans (Na+ salt form) with varying levels of acetyl and pyruvic acid substitution were prepared by culturing different strains of Xanthomonas campestris and by chemical deacetylation and depyruvylation. Oscillatory-shear measurements were used to characterize the behaviour of xanthan and guar gum alone, and of mixtures of the two in de-ionized water - the xanthan under these conditions was largely in the disordered form. The mechanical spectra of the blends resembled an 'entanglement network' system and showed some features characteristic of the individual components. However, evidence from both rheological and chiroptical measurements indicated a possible weak interaction between some low-acetyl xanthans and guar. © 1990.