Effect of high pressure treatment on the structural, mechanical and rheological properties of glucomannan gels
The influence of high hydrostatic pressure (HHP) of 100 (C100), 200 (C200), 400 (C400) and 600 MPa (C600) on the structural, physicochemical, and thermo-rheological properties of aqueous glucomannan dispersions (AGD) was studied. Each AGD was prepared with a 5% concentration of deacetylated glucomannan (GM) at pH = 11 for use in the preparation of restructured fish products. The control (0 MPa) AGD (C0) exhibited a partially crystalline GM network with a glass transition temperature (T) of ~75 °C. C0 gels at 25 °C were rigid, with high breaking force (BF), fracture constant (K) and complex modulus (G*) and low tanδ values due to the large number of physical junctions produced by complete deacetylation of the GM chains. This structural response was reflected in high water binding capacity (WBC) and colour (L*) and low cooking loss (CL). Specifically, 200 MPa reduced close packing ability in the crystalline regions, evidenced in the lower T~65 °C and resulting in lower gel strength (S), K, G* and a higher viscous component (high tanδ), thus reducing the L* value. Conversely, 600 MPa increased the degree of cross-linking in C600, reinforcing the number and extent of crystalline regions, resulting in the broadening of the O-H stretching band in the FT-IR spectrum and producing a thermoset physical network with no glass transition region. Thus, C600 gel was firmer (higher G*) with greater S, and less flexible (lower strain amplitude-γ). Consequently, depending on the textural properties desired in the final restructured fish product, the most appropriate pressure would be 200 MPa for softer final gels and 600 MPa for firmer and less deformable gels.
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | artículo biblioteca |
| Published: |
Elsevier
2016
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| Subjects: | Glassy network, High pressure, Konjac glucomannan, |
| Online Access: | http://hdl.handle.net/10261/135067 http://dx.doi.org/10.13039/501100003339 |
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| Summary: | The influence of high hydrostatic pressure (HHP) of 100 (C100), 200 (C200), 400 (C400) and 600 MPa (C600) on the structural, physicochemical, and thermo-rheological properties of aqueous glucomannan dispersions (AGD) was studied. Each AGD was prepared with a 5% concentration of deacetylated glucomannan (GM) at pH = 11 for use in the preparation of restructured fish products. The control (0 MPa) AGD (C0) exhibited a partially crystalline GM network with a glass transition temperature (T) of ~75 °C. C0 gels at 25 °C were rigid, with high breaking force (BF), fracture constant (K) and complex modulus (G*) and low tanδ values due to the large number of physical junctions produced by complete deacetylation of the GM chains. This structural response was reflected in high water binding capacity (WBC) and colour (L*) and low cooking loss (CL). Specifically, 200 MPa reduced close packing ability in the crystalline regions, evidenced in the lower T~65 °C and resulting in lower gel strength (S), K, G* and a higher viscous component (high tanδ), thus reducing the L* value. Conversely, 600 MPa increased the degree of cross-linking in C600, reinforcing the number and extent of crystalline regions, resulting in the broadening of the O-H stretching band in the FT-IR spectrum and producing a thermoset physical network with no glass transition region. Thus, C600 gel was firmer (higher G*) with greater S, and less flexible (lower strain amplitude-γ). Consequently, depending on the textural properties desired in the final restructured fish product, the most appropriate pressure would be 200 MPa for softer final gels and 600 MPa for firmer and less deformable gels. |
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