Solution characteristics of the xyloglucan extracted from Detarium senegalense Gmelin

Abstract

The macromolecular solution properties of detarium xyloglucan, a seed extract of the plant Detarium senegalense Gmelin, were investigated by steady and dynamic shear rheometry, and static light scattering. The main polysaccharide of detarium gum is a xyloglucan, consisting of a cellulosic backbone with single-unit α- d-xylopyranosyl substituents attached to carbon-6 of the glucosyl residues, and with some of the xylose residues further substituted at carbon-2 by β- d-galactopyranosyl residues. In this paper, all the semi-dilute solution characterisation work seems to be very largely consistent with much of the published data for the rheology of other polysaccharide solutions and suggests that detarium gum is a well behaved linear polymer entanglement network system. It has been established that when C < ~C∗, η sp∝C 1.3, while at C > ~2C∗, η sp∝C 4.0. The static light scattering technique was successfully applied to examine the molecular weight and architecture of the detarium xyloglucan macromolecule by employing pressure heating treatment of the samples. The scattering profile for detarium xyloglucan is not consistent with that of a linear macromolecule, but instead strongly suggests a small degree of long chain branching. The implications of this finding are discussed.