Effects of sodium carbonate and potassium carbonate on colloidal properties and molecular characteristics of konjac glucomannan hydrogels.

When konjac glucomannan (KGM) molecules are deacetylated under alkaline conditions, the aqueous KGM solution is transformed into a thermally stable gel. In this study, series of Na 2 CO 3 -induced and K 2 CO 3 -induced KGM hydrogels were prepared by deacetylation using different concentrations (0.1, 0.2, 0.3, and 0.4 M) of alkali. The hydrogels were characterized using texture profile analysis, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy, X-ray diffraction, and rheological property analysis. The data showed that KGM hydrogel formation was facilitated at all the alkali concentrations used. The mechanisms of Na 2 CO 3 -induced and K 2 CO 3 –induced KGM hydrogels formation differed slightly. The hardness, springiness, chewiness, gumminess, and storage modulus G ′ of the Na 2 CO 3 -induced KGM hydrogels initially increased and then decreased with increasing alkali concentration. However, the values of the corresponding properties of the K 2 CO 3 -induced KGM hydrogels increased with increasing alkali concentration. All the data were consistent with the structures observed using SEM. The 0.3 M Na 2 CO 3 -induced KGM hydrogel had the highest hardness and storage modulus G ′, a well-proportioned network structure, and a dense architecture; 0.3 M Na 2 CO 3 was therefore the most suitable modifier for inducing KGM hydrogel formation. [ABSTRACT FROM AUTHOR]