The effect of pH and salt on the stability and physicochemical properties of oil-in-water emulsions prepared with gum tragacanth

•The addition of NaCl does not significantly change the emulsion stability.•Gum tragacanth-coated droplets are unstable near the isoelectric point.•Confirmatory and complementary relationships between tests results were obtained. The effect of pH (2.5, 4.0 and 5.4) and salt concentration (0.0, 0.5 a...

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Bibliographic Details
Published in:Carbohydrate polymers 2016-04, Vol.140, p.342-348
Main Authors: Abdolmaleki, Khadije, Mohammadifar, Mohammad Amin, Mohammadi, Reza, Fadavi, Ghasem, Meybodi, Neda Mollakhalili
Format: Article
Language:English
Subjects:
Chemical Phenomena
Emulsion stability
Emulsions
Gum tragacanth
Hydrogen-Ion Concentration
Interfacial tension
Oils - chemistry
Particle Size
Rheological properties
Rheology
Salts - chemistry
Tragacanth - chemistry
Water - chemistry
Zeta potential
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Summary:•The addition of NaCl does not significantly change the emulsion stability.•Gum tragacanth-coated droplets are unstable near the isoelectric point.•Confirmatory and complementary relationships between tests results were obtained. The effect of pH (2.5, 4.0 and 5.4) and salt concentration (0.0, 0.5 and 1.0wt%) on the physical stability of oil-in-water emulsions stabilized with gum tragacanth were investigated during 150 days of storage. Mean droplet diameter, zeta-potential, interfacial tension and steady-shear and dynamic rheological properties were determined to achieve more information about the likely stability mechanisms. The results showed that increasing salt concentration did not have a significant effect on emulsion stability. Emulsions were highly unstable at pH 2.5, with their emulsion-stability index declining almost three times more than that of other emulsions during the storage time. Based on the size distribution data, a direct correlation was not observed between droplet size distribution and emulsion stability. Rheological analysis revealed that pH 2.5 had the lowest apparent viscosity, storage modulus, energy of cohesion (EC) and a-value, and the highest tanδ and b-value.
ISSN:0144-8617
1879-1344
DOI:10.1016/j.carbpol.2015.12.081