Preparation and characterization of heterogeneous deacetylated konjac glucomannan

Deacetylated konjac glucomannan (Da-KGM) powder was prepared in heterogeneous system. Kinetics of heterogeneous deacetylation was investigated to predict the optimum reaction conditions. The results indicated that: heterogeneous deacetylation was influenced by the kind and amount of alkali, ethanol concentration, temperature and reaction time. Meanwhile, it followed first-order kinetics and the apparent activation energy was 15.59 kJ/mol. The properties of Da-KGM were studied by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD), which proved that there was no significant difference of primary structure, thermal properties and crystal properties among Da-KGMs. The solubility was also analyzed and evaluated. As deacetylation degree (DD) increased, the solubility of KGM showed exponential decrease. In addition, lower temperature was more effective to promote the dissolution of Da-KGM.