VISCOSITY OF AQUEOUS GLUCOMANNAN BORATE COMPLEX SOLUTIONS

The viscosity of aqueous konjac glucomannan solution in the presence of borate ions was examined. The measurements were made on a rotational viscometer. The apparent viscosity of each sample was determined over the glucomannan concentration range of 0.09-0.45% w/v. In the concentration region above the critical concentration, 0.29% w/v, the viscosity was increased considerably by the presence of borate ions. This may be due to the creation of new interchain crosslinks, involving the formation of a 2:1 anionic complex (dicomplex). On the other hand, in the more dilute region the viscosity was almost independent of the presence of borate ions. In this region the formation of a 1:1 anionic complex (monocomplex) takes place predominantly and does not contribute effectively to the increase in viscosity.