Hydrocolloids:
Stabilisers, Thickeners and Gelling Agents > GUM TRAGACANTH
GUM TRAGACANTH
Application
APPLICATION
FUNCTION
Icings
Moisture control and maintain pliability
Oil and flavour emulsions
Viscosity control and emulsification
Frozen desserts
Ice crystal control
Chemistry Gum tragacanth (E413) is the
natural exudate gum obtained from small shrubs of the
Astragalus species, mainly located in
southwest Asia.
Gum tragacanth consists of two fractions: an insoluble component
generally called bassorin (60-70%) of the gum), and a water-soluble
component generally called tragacanthin. The ratio of these
components varies from species to species and partly explains
the viscosity differences in commercial samples.
Properties Tragacanth gums hydrate in water
to give viscous, slightly long solutions and pastes. Solutions
are pseudoplastic
with a reversible decrease in apparent viscosity as shear
rate is raised. The high viscosity at low shear, coupled
with charge repulsion effects, suspend fine particles in
solution and help stabilise oil in water emulsions. The
maximum viscosity is found at pH 8 but the gum is most
stable
at its natural pH of 5.
Dispersions of Tragacanth are more stable to acids than
those of other gums. The addition of small quantities of
sugar does not unduly affect the viscosity, however the
addition of salt however lowers the viscosity. Gum Tragacanth
shows good stability to freeze-thaw cycling. Autoclaving
lowers the viscosity of properly dispersed samples.
Gum
Tragacanth reduces interfacial tension and increases solution
viscosity, which helps stabilise oil in water emulsions.
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