Influence of dehulling pretreatment on physicochemical properties of Gleditsia sinensis Lam. gum

The seeds of Gleditsia sinensis Lam., widespread in China, are an important source of galactomannans. G. sinensis gum was extracted from whole seeds using baking, boiling water and acid dehulling pretreatment, respectively. The physicochemical properties of the three isolated G. sinensis gums were studied to evaluate three pretreatment methods. The results illustrated that the properties of G. sinensis gum were significantly influenced by dulling method (p < 0.05) including the yield, M/G ratio, viscosity, chemical composition and molecular weight. Power-law model (View the MathML source) was applied to the rheological measurements, which indicated that solutions of Gb, Gw and Ga gum behaved as pseudoplastic fluids at the concentration of 0.5% (w/v). The gum obtained by acid pretreatment (Ga) had the lowest yield of 20–24% (w/w). However Ga showed a pronounced shear-thinning behavior and particularly higher viscosity compared with the gums extracted by baking pretreatment (Gb) and boiling water dehulling method (Gw). The mannose to galactose ratios (M/G ratio) for Gb, Gw and Ga were found to be 4.5, 4.4 and 6.9, respectively. The highest molecular weight of 3.31 × 106 Da was observed for the galactomannans of Gb.