Chemical and physical characterization of Konjac glucomannan-based powders by FTIR and 13C MAS NMR

Konjac glucomannan (KGM) is extracted from Amorphophallus konjac tuber and composed of beta-1,4 linked D-mannose and D-glucose. We aimed to produce and characterize KGM-based powders manufactured from dried (55 degrees C-KF55 and 75 degrees C-KF75) konjac tubers and compare to a commercial konjac glucomannan (CKG) powder. Structural characteristics on molecular, compositional, and microstructure levels as well as rehydration properties were assessed. Both compositional analysis as well as FTIR and 13C MAS NMR spectral analysis demonstrated a higher amount of protein than KF55 sample. The ratio between the two monomer units (D-mannose and D-glucose) was 1.6:1 in KF75, whereas it was 1.4:1 and 1.2:1 for KF55 and CKG, respectively, indicating slightly higher Man:Glc ratios in the KF samples. Decreased rehydration properties and flow index behavior (in solution) were observed in the konjac flours. Thus, differences were significant; konjac flours also presented good functionality, thereby, a good alternative to be used as hydrocolloid in food formulations. (C) 2019 Elsevier B.V. All rights reserved.