Hydration properties and mesoscopic structures of different depolymerized konjac glucomannan: Experiments and molecular dynamics simulations

Abstract

The degradation of Konjac glucomannan (KGM) can greatly change its characterization and impact its applications in the food industry. KGM with varying hydration properties can be diversely utilized in the food sector. To investigate the variability between the structure and properties of KGM with different depolymerized degree (DP), the different depolymerized konjac glucomannan (DKGMx) was prepared by enzymatic digestion. Hydration properties were assessed using solubility index (WSI), water absorption index (WAI), apparent viscosity, hydrophilic angle, hygroscopicity, and rheological properties; thermal stability was evaluated through thermo-physical analysis (TG); changes in structure were analyzed using gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scanning electron microscopy imaging (SEM), and molecular dynamics simulation. These findings indicated that that as DP decreased, DKGMx exhibited lower molecular weight, decreased the swelling capacity and apparent viscosity, decreased the hydrophilic angle, increased moisture absorption capacity, and water solubility, altered the crystallized region, decreased thermal stability, and changed the rheological properties. Molecular dynamics simulations revealed that the alteration in degree of polymerization (DP) induced changes in chain flexibility, hydrogen bond count. Molecular simulation and macroscopic experiments elucidated how DP led to changes in the hydration properties of KGM at a mesoscopic scale by altering its chain structure and interaction forces.