Structural elucidation of galactomannan from seeds of Crotalaria mucronata Desv. by atomic force microscopy

A non-ionic water-soluble galactomannan, isolated from the seed endosperm of Crotalaria mucronata Desv., may be an ideal thickener to increase food viscosity. The present study hypothesized that the viscous property of Crotalaria galactomannan may be associated with its spatial structure. Therefore, the structure of Crotalaria galactomannan was elucidated using an atomic force microscope. The results of the present study demonstrated that the polysaccharide consisted of a D‑mannose backbone with D‑galactose branches, and the D‑mannose/D‑galactose ratio was 2.375:1. In the three‑dimensional structure of Crotalaria galactomannan, the helix was a common secondary structure, containing numerous ring structures of different sizes. In addition, multiple helixes may link together via hydrogen bonding and van der Waals forces, forming aggregations with small rings or spiral windings. The results of the present study indicated that the multiple‑branching construction of Crotalaria galactomannan may underlie its viscosity‑enhancing properties in the water phase.