Gum Tragacanth (E413) is a natural plant
exudate traditionally used to stabilise emulsions.
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.
Gum Tragacanth has fallen out of favour with food processors in recent times
mainly because of significant price fluctuations associated with supply issues.
