Salt-induced thermal gelation of xyloglucan in aqueous media.

ABSTRACT

The influence of Na2SO4 as a kosmotropic salt on the thermogelation of xyloglucan (XG) solutions was measured by rheology. The gelation occurred at lower temperatures and shorter times when the salt concentration was increased above 0.5 mol.L-1. For Na2SO4 concentrations equal to 1 mol.L-1, a not thermoreversible elastic hydrogel was obtained. Salts containing various types of anions were used, and it was observed that SO42-, HPO42- and H2PO4- promoted the formation of a gelled network. The gel structure was observed using confocal laser scanning microscopy and scanning electron microscopy. In XG containing SO42 at 1 mol.L-1aggregates and gels were formed by interconnected sub-micrometer XG particles. Increasing the concentration of SO42- led to conformation changes in the XG, from a twisted/helical to an extended/flat conformation, as observed using circular dichroism. The naturally occurring hydrophobic sequences promoted an economically feasible XG gelling that may produce thermo and kosmo-sensitive hydrogels.