Characterization of galactomannans derived from legume endosperms of genus Sesbania (Faboideae)

Galactomannan polysaccharides extracted from seed endosperms of 12 species of the genus Sesbania (legume subfamily Faboideae) have been characterized by size-exclusion chromatography, dilute-solution viscometry, and oscillatory-shear rheology to determine their potential as aqueous thickeners. The molecular composition and chain-length distribution were found to be nearly identical, and thus galactomannans within this genus are presumed to share a common molecular structure (DSgal ≈ 0.7, Mw ≈ 2.5 × 106, PDI ≈ 2). Solutions at c > c* exhibited shear-thinning behavior, and strong dependence of viscosity on concentration (η ∼ c5). Purified samples had Huggins' constants near 0.5, and negligible surface activity based on pendant drop tensiometry. Seed characteristics such as shape, mass, and endosperm content were also assessed, and based on this investigation, some Sesbania legume endosperms are advantageous for industrial processing and could be adapted for guar gum replacement.