Viscosity and Gel Formation of a Konjac Flour from Amorphophallus oncophyllus

The influences of different variables on the viscosity and gel formation of the konjac flour produced from Amorphophallus oncophyllus have been studied. At the concentration studied, the 1.5% konjac flour yielded a viscous solution than that of 0.5% konjac flour. The viscosity of konjac flour solution were unaffected by pH (pH 2 to pH 8), salt concentration (0-10% w/v), and high acid (pH 3.5) / high temperature (70°C) condition for 5 hr. With higher sucrose concentration, the viscosity of konjac flour solution tended to decrease. The konjac flour maintained its viscosity under sterilization process (121°C at 15 lb/in) for 30 min, whereas the viscosity decreased in the same condition with the presence of 2.5% NaCl. The considerable increase in viscosity were observed for the mixtures of konjac flour / rice flour, konjac flour / wheat flour, and konjac flour / corn flour. For gel formation studied, the hydrocolloids which synergistically interacted with konjac flour to form gels were xanthan gum, κcarrageenan, and agar. The texture of these gels were varied with konjac flour/synergistic hydrocolloids ratios.