Effect of preparation on the dissolution rate of konjac glucomannan

The preparation of konjac glucomannan(KGM) using water-extracting alcohol-precipitating and milling KGM in 50% ethanol was investigated. The results show that the purity, apparent viscosity, weight average molecular weight of KGM, which is obtained using two methods, are similar. The KGM dissolution rates are significant different got from different methods. KGM dissolution rates obtained using milling KGM in ethanol are 26.4 mg/mL·h, and KGM dissolution rates obtained using water-extracting alcohol-precipitating method are 10 mg/mL·h. The KGM structure was characterized using FT-IR, X-ray diffraction and SEM. The results of IR spectrum, X-ray diffraction and SEM microphotographs show that expanding, rearrangement, crimping, interlacing and interaction between the molecular chains have happened in molecular of KGM obtained using water-extracting alcohol-precipitating method. In this process, KGM molecular chains expended in aqueous solution, and crimped when precipitated from ethanol. This preparation method resulted in significant changes of dissolution rate.