Effects of the lyotropic series salts on the gelation of konjac glucomannan in aqueous solutions

Effects of Lyotropic series salts on the gelation behavior of konjac glucomannan (KGM) in aqueous solutions were studied by means of rheometry and electron spin resonance (ESR). Rheological measurements showed that sulfate alone, heretofore never reported, was capable of inducing KGM form a thermally irreversible gel rather than via deacetylation that has been the approbatory origin when the commonly alkaline coagulant of Na2CO3 is used. The increase in rotational correlation time that scales with the microviscosity indicated reduced mobilities of KGM chains upon addition of Na2SO4, in agreement with the rheological results. In the presence of Na2CO3, salting-out salts facilitated the gelation, whereas salting-in salts assisted the gelation at low salt concentrations but suppressed it at high salt concentrations. It was suggested that the Na2CO3 be also of salting-out effect in addition to facilitating the deacetylation. of KGM chains. (c) 2008 Elsevier Ltd. All rights reserved.