Gelation behaviour of konjac glucomannan with different molecular weights

The deacetylation and gelation of konjac glucomannan (KGM) following alkali addition was investigated by Fourier transform infrared, while the rheological properties of KGM with different molecular weights were studied by dynamic viscoelastic measurements in shear mode and penetration force tests. I...

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Bibliographic Details
Published in:Biopolymers 2001-07, Vol.59 (1), p.38-50
Main Authors: Zhang, H., Yoshimura, M., Nishinari, K., Williams, M. A. K., Foster, T. J., Norton, I. T.
Format: Article
Language:English
Subjects:
Acetylation
deacetylation
disentanglement
dynamic viscoelasticity
gelation mechanism
Gels - chemistry
konjac glucomannan
Mannans - chemistry
Molecular Weight
Rheology
slippage
Spectroscopy, Fourier Transform Infrared
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Summary:The deacetylation and gelation of konjac glucomannan (KGM) following alkali addition was investigated by Fourier transform infrared, while the rheological properties of KGM with different molecular weights were studied by dynamic viscoelastic measurements in shear mode and penetration force tests. It was found that gelation occurred after significant deacetylation had taken place. Rheometrical studies revealed that KGM with different molecular weights exhibited different gelation characteristics in small amplitude oscillatory shear flow. For the samples of fractionated KGM with lower molecular weights, a decrease in both the storage shear modulus (G′) and loss shear modulus (G″) was observed during gelation at temperatures above 75°C. It is suggested that the decrease results from the wall slip between sample and measuring geometry owing to a rapid gelation process with syneresis and/or disentanglement of molecular chains adsorbed on the surface of parallel plates from those located in the bulk. Penetration force tests were employed to confirm the occurrence of slippage and thereby no decreases in rigidity of samples were observed during gelation. For the native KGM samples decreases in G′ and G″ during gelation were not observed, and it is suggested that this is due to the effect of the higher molecular weight and increased solution viscosity of these samples on the gelation kinetics. © 2001 John Wiley & Sons, Inc. Biopolymers 59: 38–50, 2001
ISSN:0006-3525
1097-0282
DOI:10.1002/1097-0282(200107)59:1<38::AID-BIP1004>3.0.CO;2-A