The structures of konjac glucomannan (KGM) and deacetylated konjac glucomannan (Da-KGM) were analyzed using Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffraction analysis, and the water-holding capacity and viscosity of KGM and Da-KGM were compared. With cellulose as a control, an in vitro simulation of the human gastrointestinal tract was prepared, and the fat- and cholesterol-adsorption capacities of KGM and Da-KGM were compared. The results showed that, after deacetylation, the characteristic absorption peak of the acetyl group at 1733 cm-1 of KGM disappeared, the degree of crystallinity increased, the water holding capacity decreased by 83.7%, and the characteristic high viscosity was lost. Compared with cellulose, KGM had a higher capacity to adsorb fat and cholesterol, and the total adsorption capacity increased with increasing sample mass, adsorption time, and cholesterol concentration. Compared with natural KGM, Da-KGM exhibited a decreased capacity to adsorb fat and cholesterol. This might be due to the strengthening of hydrogen bonds between KGM molecular chains, leading to a reduction in the number of binding sites between KGM and lipids and the disappearance of the characteristic high viscosity, causing a decrease in the capacity of KGM to directly bind with lipids. These results indicated that the lipid-binding capacity of KGM in the intestinal tract was reduced after deacetylation, and that its physiological function (weight loss effect) might be affected.
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