A one-step procedure for elevating the quality of konjac flour: Azeotropy-assisted acidic ethanol

Abstract

Konjac glucomannan (KGM), mainly contained in konjac flour (KF), has been widely applied in food industry. However, commercial KF is usually light-colored with low KGM content, fish-like smell and low viscosity. In this paper, a one-step procedure, azeotropy-assisted acidic ethanol, was explored to elevate the overall quality of KF. Composition, transparency, color and odor evaluation, rheological properties and morphology of all the disposed KF were measured to evaluate the quality as compared with commercial KF. KF with 90% (w/w) KGM content could be easily obtained by pH regulation. At the high pH level (4.5–5.5), the quality of disposed KF was greatly improved, included by purity, transparency, and odor evaluation. Both the rheological properties and morphology observation verified the elevated effect. But the quality of KF was inclined to be poor at low pH level (2.5–4.0) due to KGM hydrolysis. The obtained white-colored Y4.5 with light fish smell tended to possess the highest viscosity and stability. The results illustrated washing by acidic ethanol at azeotropy point was feasible to effectively improve the quality of KF. The method has not only broadened KF potential application in food field, but also enriched the knowledge of its quality elevation.