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Rheological properties of Cedrela odorata gum exudate aqueous dispersions

Abstract:

Rheological studies of Cedrela odorata gum aqueous dispersions demonstrated viscoelastic properties. Mechanical spectra derived from small amplitude oscillatory shear (SAOS) results support the onset of gel-like structure at given conditions (10% w/v, 20 °C). The increase in the storage and loss moduli, along with the drop in their frequency dependence, observed at higher gum concentrations, indicates a slower relaxation mechanism, which may be related to the increasing number and structural complexity of transient junction zones among macromolecules. The transition from gel-like to sol-like structure, at higher temperature, was detected from SAOS results. The flow behaviour of the aqueous gum dispersions under steady shear is highly non-Newtonian and can be modelled by the Sisko equation. The Cox-Merz rule was found to fail at critical gum concentration for the onset of gel-like behaviour and also at a temperature slightly above the gel-sol transition. C. odorata gum aqueous dispersions may have interesting applications as stabilisers of emulsions and suspensions on account of their rheological behaviour. © 2008 Elsevier Ltd. All rights reserved.