Rheological properties and surface tension of Acacia tortuosa gum exudate aqueous dispersions
Abstract:
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. © 2007 Elsevier Ltd. All rights reserved.
Año de publicación:
2007
Keywords:
- Surface tension
- Acacia tortuosa
- Gum exudate
- Rheological properties
Fuente:
Tipo de documento:
Article
Estado:
Acceso restringido
Áreas de conocimiento:
- Ciencia de los alimentos
- Reología
- Bioquímica
Áreas temáticas:
- Química orgánica
- Bioquímica
- Plantas conocidas por sus características y flores