Rheological and microstructural investigation of oat β-glucan isolates varying in molecular weight

Jacob K. Agbenorhevi, Vassilis Kontogiorgos, Andrew R. Kirby, Victor J. Morris, Susan M. Tosh

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Abstract

The rheological properties and microstructure of aqueous oat β-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by 13C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the β-glucans dispersions was also examined by atomic force microscopy (AFM). The samples with β-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([η]) and critical concentration (c) in the range of 142-2800×103g/mol, 1.7-7.2dl/g and 0.25-1.10g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the β-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW samples. The Cox-Merz rule was applicable for the lower molecular weight samples at higher concentrations whereas the high molecular weight sample deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the samples investigated and has been linked to the rheological behaviour of the samples.

Original languageEnglish
Pages (from-to)369-377
Number of pages9
JournalInternational Journal of Biological Macromolecules
Volume49
Issue number3
Early online date26 May 2011
DOIs
Publication statusPublished - 1 Oct 2011
Event16th International Gums and Stabilisers for the Food Industry Conference - Wageningen, Netherlands
Duration: 28 Jun 20111 Jul 2011
Conference number: 16

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