Dissolution behavior of deacetylated konjac glucomannan in aqueous potassium thiocyanate solution at low temperature

Abstract

Deacetylation adversely affected the solubility of konjac glucomannan (KGM) in water; however, KGM with different degrees of deacetylation could be well dissolved in 9 wt% potassium thiocyanate (KSCN) solution at −4 °C. The dissolution behavior and the mechanism of the dissolution of deacetylated KGM (da-KGM) were studied in detail. The results from differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and viscometry demonstrated the existence of KSCN hydrate at low temperatures. With increasing KSCN concentration, the number of bound water molecules per KSCN molecule decreased. Low temperature aided the disintegration of da-KGM molecular chains, prevented the approach of da-KGM molecules toward each other and prompted the binding of da-KGM and KSCN hydrate to form a larger complex by hydrogen bonding. The result of CP-MAS ¹³C NMR spectroscopy indicated that KSCN could be a non-derivative solvent of da-KGM since neither obvious changes in molecular chain structure occurred, nor new derivatives generated after the dissolution of da-KGM.