Effects of Deacetylated Konjac Glucomannan on Gelatinization and Rheological Properties of Potato Starch

Konjac glucomannan with different deacetylation degrees of 20%, 45%, 70% and 90% was added to the raw material potato starch to form mixture. The gelatinization and rheological properties of the mixture were studied. The results showed that as the deacetylation degree of konjac glucomannan increased, the gelatinization temperature of the mixture shifted slightly to a higher temperature (from 66.0℃ to 66.5℃), and the gelatinization enthalpy went down from 10.1 J/g to 8.9 J/g. Static rheological results showed that the mixture made of deacetylated konjac glucomannan and potato starch was a pseudoplastic non-Newtonian fluid with an obvious shear thinning phenomenon. The power law equation fitting results found that with the increasing of the deacetylation degree of konjac glucomannan, the k value of the consistency coefficient of the mixture increased from 128.8 to 694.4, and the flow characteristic index n value declined from 0.4711 to 0.3879. Dynamic rheological results presented when the deacetylation degree of konjac glucomannan increased from 20% to 90%, the An value representing the gel strength of the mixture increased from 236.7 to 2468.9. It indicated that konjac glucomannan with a higher deacetylation degree contributed significantly to the gel strength of the mixture.