Rheological properties and surface tension of Acacia tortuosa gum exudate aqueous dispersions
Steady shear flow properties of Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20 °C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newto...
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Published in | Carbohydrate polymers Vol. 70; no. 2; pp. 198 - 205 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
Elsevier Ltd
20.09.2007
Elsevier Science |
Subjects | |
Online Access | Get full text |
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Summary: | Steady shear flow properties of
Acacia tortuosa gum aqueous dispersions at different concentrations (15–40% w/v) were studied at 20
°C using a controlled shear rate Couette rheometer and Mooney–Ewart sensor systems. Flow curves showed shear thinning non-Newtonian behaviour with a tendency to a Newtonian plateau at high-shear rate. The results obtained fitted the Sisko model very well. The influence of temperature (5–40
°C) on the flow curves was studied at given gum concentration (40% w/v). The infinite-shear rate Newtonian viscosity derived from the Sisko model fitted an Arrhenius-type equation. A controlled stress rheometer was used to conduct small amplitude oscillatory shear tests with the double cone geometry on
A. tortuosa gum dispersion (40% w/v). It was clearly observed that the gum dispersion exhibited viscoelastic properties in a given temperature range (5–25
°C). The elastic component was always higher than the viscous one. The frequency dependence of the dynamic moduli and the failure of the Cox–Merz rule supported the existence of a soft gel-like structure which weakened with temperature. The surface tension of
A. tortuosa aqueous solutions was measured in a concentration range (0.01–1.5% w/v). The equilibrium value reached at (0.5% w/v) was (42.6
mN/m), which is significantly lower than the corresponding to
A. senegal gum (46.9
mN/m). The rheological behaviour and surface tension of
A. tortuosa gum suggest that it may compete with arabic gum in some industrial applications. |
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Bibliography: | http://dx.doi.org/10.1016/j.carbpol.2007.03.018 |
ISSN: | 0144-8617 1879-1344 |
DOI: | 10.1016/j.carbpol.2007.03.018 |