Comparison and characterization of galactomannan at different developmental stages of Gleditsia sinensis Lam

Pods from a Gleditsia sinensis Lam. tree were collected and the galactomannan content and other properties were determined at their different developmental stages. In green and immature seed, galactomannan was substituted to a great extent with a mannose to galactose (M/G) ratio of 2.4 from crude polysaccharides. During late galactomannan deposition, it was substituted to a lower extent and this ratio increased rapidly, reaching a M/G ratio of 3.1. Average molecular weight (M_w) of the extracted polysaccharides first increased, reached the maximum (1.19 × 10⁶) at 17 weeks after flowering (WAF), and then decreased. These changes might result from primary galactomannan biosynthesis and from galactose removal by α-galactosidase in the endosperm. The solubility of crude polysaccharides decreased with increased M/G ratio and maximum solubility was more than 89% that collected at 13 WAF. Rheological properties showed that apparent viscosity was largely influenced by the molecular weight and M/G ratio of galactomannans.