CIDCA   05380
CENTRO DE INVESTIGACION Y DESARROLLO EN CRIOTECNOLOGIA DE ALIMENTOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Viscoelastic characterization of fluid and gel like food emulsions stabilized with hydrocolloids
Autor/es:
GABRIEL LORENZO, NOEMI E. ZARITZKY , ALICIA N. CALIFANO
Lugar:
Atenas
Reunión:
Congreso; 11th International Congress on Engineering and Food; 2011
Resumen:
Food emulsions exhibit a great diversity of rheological characteristics,
ranging from low-viscosity Newtonian liquids to viscoelastic and plastic
materials. Hydrocolloids are usually key components in food emulsions to deal
with creaming instability. There is a growing emphasis on understanding the
colloidal basis of the rheology of food emulsions. Viscoelastic measurements
are appropriate tools for obtaining information about the microstructure of the
system related to the organization of the macromolecules in the medium. The existence of a broad distribution of
relaxation times in polymeric materials can be represented by the
mechanical relaxation spectrum derived from experimental values of the dynamic moduli G' (storage modulus) and
G" (loss modulus).
The objectives of the present work were: a) to determine the
viscoelastic behavior of two different low in fat oil-in-water food emulsions:
a gel like and a pourable fluid type emulsions stabilized with hydrocolloids
(gellan gum and xanthan-guar mixtures respectively) b) to model and predict the
mechanical relaxation spectrum for both emulsions and continuous aqueous
phases. Low-in-fat emulsions (20g/100g) were analyzed in two distinct
formulations, a pourable fluid dressing type emulsion and an emulsion-filled
gel .Oil-in-water emulsions
were prepared using sunflower oil (20 wt.%) and Tween 80 (1 wt.%). Fluid
emulsions containing xanthan and guar gums were formulated using a synergistic
ratio 7:3, with total hydrocolloid concentration ranging between 0.5 to 2 wt%.
The aqueous phases contained NaCl (2 wt.%) and acetic acid (2 wt.%).The effect of
hydrocolloids was studied using oscillatory measurements (G? and G?? vs. frequency) within the linear
viscoelastic range (LVR) previously
determined by stress-sweeps. Time-Concentration Superposition principle was
applied to find the master curves that describe the mechanical spectra of the
viscoelastic materials. Superposition allows to obtain a wide spectrum of
nearly ten decades of frequencies in emulsions containing xanthan?guar
mixtures, whereas gellan gum systems did not show a significant frequency
displacement.Viscoelastic behavior of the systems was satisfactorily modeled
using Baumgaertel-Schausberger-Winter (BSW) equation. This empirical model was
used to predict the mechanical relaxation spectrum for both emulsions and
continuous aqueous phases. Validation of the predicted spectra was carried out
through creep compliance data for emulsion-filled gels and steady-state flow
curves for emulsions containing xanthan?guar mixtures