Rheological Property of Hydrolyzed Konjac Glucomannan

Abstract

Konjac glucomannan (KM) is a water soluble glucomannan with high molar mass. KM aqueous solution shows extremely high viscosity. KM can be depolymerized by chemical hydrolysis. The molar mass of hydrolyzed KM decreased with increase of acid concentration and hydrolysis time. The acid hydrolysis led chain scission of KM, but introduced no significant new chemical groups into the structure. KM molecular chain was hydrolyzed randomly by acid hydrolysis. The viscosity of KM aqueous solutions decreased with decreasing molar mass. KM solution changed to Newtonian fluid with decreasing molar mass at low concentration. KM with molar mass less than 320 kDa was Newtonian fluid in semi-dilute region. KM aqueous solution showed two kinds of critical overlap concentration of C* and C**. C* is onset of shrinkage of the polymer coils and C** is the critical concentration to attain their limiting size. The overlapping and entanglement of KM chains with high molar mass occurred at lower concentration as compared to those of KM with low molar mass.