Physical, chemical, and rheological properties of konjac glucomannan phosphate ester

Konjac glucomannan phosphate ester (KGMP) is a chemically modified version of konjac glucomannan (KGM) designed to address the shortages of KGM, such as low solubility in water, lack of stability in solution, and poor fluidity. In this paper, the physical, chemical, and rheological properties of the KGMP with various degrees of substitution (DS) were investigated. The KGMPs were prepared by a semi-dry method with vacuum-microwave assistance. The structure of the KGMPs was validated using Raman and solid-state 31P nuclear magnetic resonance (NMR) spectroscopy. Scanning electron microscopy (SEM) revealed that the structural change of phosphate groups primarily occurred on the surface of KGM granules, while X-ray diffraction (XRD) demonstrated that phosphate modification did not change the crystalline type of KGM. Rheological analysis indicated that KGM and KGMP sols exhibit a non-Newtonian fluid behavior, and the Carreau model is suitable for explaining the steady-state rheological behavior of KGM and KGMP with different DS. The viscosity of the KGMPs was sensitive to temperature and had good shear resistance. These findings suggest that the KGMP has potential applications in developing temperature-sensitive matrix materials, gelling food and water-retaining agents.