Hydrolysis of Konjac Flour under Subcritical Water Conditions

Abstract

Konjac glucomannan-derived oilgosaccharides are a potential dietary fiber source. In this study, 5 g/L konjac flour solution was treated under subcritical water conditions at 160 0C, 180 0C, 200 0C, and 240 0C for 10 min in a batch-type reactor. The solutions showed an immediate decrease in viscosity (from 150 to less than 10 mPa.s) and increases in reducing sugar contents (from 0.1 to 2.3 g/L) after treatment, indicating that glucomannan polymers were hydrolyzed to shorter chains. The treatment at 220 0C resulted in carbohydrate yield of greater than 46% and considerably higher oilgosaccharide contents than the other treatments. Subcritical water treatment was demonstrated to be a promising method for preparing oilgosaccharides from konjac flour.