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Structural and mechanical characterization of κ/ι-hybrid carrageenan gels in potassium salt using Fourier Transform rheology

Authors
Journal
Food Hydrocolloids
0268-005X
Publisher
Elsevier
Publication Date
Volume
23
Issue
8
Identifiers
DOI: 10.1016/j.foodhyd.2009.06.008
Keywords
  • Fourier Transform Rheology
  • κ/ι-Hybrid Carrageenan
  • Strain Hardening
  • Colloidal Gel
  • Cellular Microstructure
Disciplines
  • Engineering

Abstract

Abstract The mechanical and structural properties of κ/ι-hybrid carrageenan gels obtained at various concentrations in the presence of 0.1 m KCl were studied with Fourier Transform rheology (FTR) and cryoSEM imaging. FTR data show that gels formed at concentration below 1.25 wt% exhibit a strain hardening behavior. The strain hardening is characterized by a quadratic increase of the scaled third harmonic with the strain and a third harmonic phase angle of zero degree. Both features are weakly depending on the concentration and conform to predictions from a strain hardening model devised for fractal colloidal gels. However, the phase angle of the third harmonic reveals that κ/ι-hybrid carrageenan gels obtained at higher concentrations show shear thinning behavior. Colloidal gel models used to extract structural information from the concentration scaling of gel equilibrium shear modulus G 0 and the strain dependence of FTR parameters suggest that κ/ι-hybrid carrageenan gels are built from aggregating rod-like strands (with fractal dimension x = 1.13) which essentially stretch under increasing strain. The mechanically relevant structural parameters fairly match the gel fractal dimension ( d = 1.66) obtained from the cryoSEM analysis.

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