RHEOLOGICAL PROPERTIES OF WELAN GUM IN AQUEOUS-MEDIA

The flow behavior and dynamic viscoelasticity of welan gum solutions were measured with a rheogoniometer. The welan gum showed shear-thinning behavior at a concentration of 0.1%, but plastic behavior above 0.3% at 25-degrees-C. The dynamic viscoelasticity increased with increasing concentration, and was scarcely changeable with increasing temperature even at 80-degrees-C. Gelation did not occur even in a polysaccharide concentration of 1.0% at low temperature (0-degrees-C). An increase of the dynamic modulus was not observed on the addition of CaCl2 (6.8 mM). The dynamic viscoelasticity of welan gum solution was scarcely changeable in a wide range of pH from 2 to 12. The dynamic modulus was also scarcely changeable on addition of urea (4.0 M). Possible mode of intramolecular associations between the OH-4 of the D-glucosyl residue and the adjacent hemiacetal oxygen atom of the L-rhamnosyl residue, and between the methyl group of the L-rhamnosyl residue and the adjacent hemiacetal oxygen atom of the D-glucosyl residue were proposed.