THE ISOLATION AND CHARACTERIZATION OF A WATER EXTRACT OF KONJAC FLOUR GUM

An aqueous extract from konjac flour was dried, milled and redispersed in water, prior to its characterization by viscometry and rheometry. The rate of change of relative viscosity with reciprocal absolute temperature was of a magnitude less than that of some other polar polysaccharides by a factor approximating 2. The volume-concentration relationship was non-linear in water, but linear in 0.04 m tartaric acid. The hydrophilicity of this extract in 0.04 m tartaric acid was only 0.68 g g-1 solute/100 g dispersion, much less than that of many of the commonly used polysaccharides. The intrinsic viscosity was 1320 ml g-1, among the highest of the polysaccharides. Considering the relatively low water affinity, the high viscosity of the konjac extract was attributed mostly to solute-solute interaction, rather than to hydration, at functional use-levels. The dried, redispersed extract was characterized in both steady and dynamic shear by the Carreau and Cross equations, and by the Cox-Merz rule. Deviation from the Cox-Merz rule was attributed to molecular associations of time scales longer than non-specific physical entanglements.