Gum tragacanth is a viscous, odorless, tasteless, water-soluble mixture of polysaccharides obtained from sap which is drained from the root of the plant and dried. The gum seeps from the plant in twisted ribbons or flakes which can be powdered.
Gum tragacanth is the dried gum exuded by the stem elements of Astragalus gummifer or other Asiatic species of Astragalus. This plant is a small, low, bushy perennial shrub characterized by a relatively large tap root, which, along with the branches, is tapped for the gum.
The plants grow wild in certain sections of Asia Minor and in the arid and mountainous regions of Iran, Syria and Turkey. However, Iran is the best commercial source and supplies the highest quality gum. The gum exudes spontaneously from breaks or wounds inflicted in the bark of the shrubs. The exudate of gum is in the form of ribbon or flake, which becomes brittle on drying. The collection season extends from May to September for ribbons and from August to November for flakes. After collection, the gum is sorted by hand into various grades of ribbons and flakes.
The various grades of gum received are prepared for marketing. The process includes grading, cleaning, milling, sizing and blending for specific viscosities to meet particular customer requirements. Quality control of viscosity and mesh specifications is of utmost importance in producing uniform gums for industry. To assure customer satisfaction, the gum is further processed to conform to sterility standards when required.
Powdered ribbon gum tragcanth is white to light yellow in color, while powdered flake gum is yellowish white to tan. The gum is odorless and has an insipid taste.
Gum tragacanth swells rapidly in either cold or hot water to form highly viscous colloidal sols or semi-gels, which act as protective colloids and stabilizing agents. The water solubility of gum tragacanth results form carboxyl group, which as salts have strong solubilizing action. Gum tragacanth is insoluble in alcohol and other organic solvents. It can tolerate low percentages of alcohol or glycols when in water solution.
The viscosity is the most important property of gum tragacanth solutions. The viscosity of the gum solution depends on the grade of the gum. The viscosity of 1% solutions may range from 100 to 3800 cps at 60 rpm using a Brookfield viscometer. The solution viscosity reaches a maximum in 24 hrs. At 25C, but this can be obtained in about 2 hours at 50C. A 2-4% concentration of the gum forms a thick gel.
Prepartion Of Solution
The powdered gum tragacanth shows a tendency toward lumping when added to water. The best procedure to overcome this to use vigorous agitation with a high speed mixer. Where possible, it is better to pre-wet the gum with a wetting agent such as glycerin, propylene glycol, or alcohol. Even if lumps form, they will go completely into solution on standing. When other ingredients such as sugar are included in the formulation, it is better to dry blend them with the gum before adding to the water. Solution is usually complete after one hour.
The uses of gum tragacanth depend on its action as an effective emulsifying and suspending agent with an extremely long shelf life and stability to heat and acidity.
Food Salad Dressings:-
Because of its relative stability to heat, acidity and aging, gum tragacanth is used as a thickener and stabilizer in pourable salad dressings of the regular and low calorie types.
Used for stabilization and emulsification as well as acid resistance and long shelf life.
Used as an emulsifier and thickening agent. In fruit fillings it serves as a thickener or suspending agent and forms a creamy filling with good shine, transparency and long shelf life.
Used to increase viscosity and provide a mixture, which is stable and is applied in most preparations of flavor oil with water.
Used as a binder in the manufacturing of candy cigarettes and lozenges.
Gum tragacanth is used in a variety of medicinal emulsion mixtures, jellies and creams as an excellent suspending and emulsifying agent.
Used as a suspending agent in various toothpaste to form a creamy and brilliant product. Its long shelf life and film forming properties make it useful in hair lotions hand lotions and creams.
Gum tragacanth is compatible with other plant hydrocolloids as well as carbohydrates and proteins. Viscosity is most stable at pH 4 to 8. The gum is quite stable at higher pH as well as down to pH 2. Gum tragacanth is compatible with relatively high salt concentrations and with most other natural and synthetic gums. The addition of strong mineral and organic acids causes a drop in the viscosity of the solution. However, gum tragacanth is the most resistant of the hydrocolloids and is chosen for use under highly acidic conditions. Divalent and trivalent cations can cause a viscosity drop.
Gum tragacanth, like other plant hydrocolloids, is subject to bacterial attack. Glycerol or propylene glycol, at 94 ml/liter serve as excellent preservatives in many emulsions. Gum tragacanth jellies are preserved with benzoic acid as well as sodium benzoate at less than 0.1% concentration when used below pH 6. A combination of 0.17% methyl and 0.03% propyl para-hydroxybenzoates is also effective.
Gum tragacanth is used in print pastes and sizes because of its goods release properties. It is used for stiffening silks and crepes and in the dressing of leather.
Used as a binder and acts as a suspending agent prior to the firing of the ceramic in the furnace.
Used in the manufacturing of certain types of emulsion polishes for furniture, floor and automobiles.CIGARS used as an adhesives for reconstituted cigar wrapper leaves.
Gum tragacanth consist of a mixture of water-insoluble polysaccharides, bassorin which constitutes about 60-70 % of the gum, and water-soluble polysaccharides, tragacanth in which yield on hydrolysis, L-arabinose, L-fucose, D-xylose, D-galactose and D-galacturonic acid. These acidic components are largely present as calcium, magnesium, and potassium salts. In addition, the gum contains small amounts of cellulose, starch portion, and ash. The soluble portion of the gum gives a colloidal hydrosol solution with water, while the insoluble fraction swells into a gel. Gum tragacanth solutions are acidic usually in the pH range 5-6. The maximum initial viscosity of gum tragacanth is at pH 8, but maximum stable viscosity is at about pH 5. The molecular weight of the gum is 840,000, and the molecules have an elongated shape, 4500A, by 19A, which account for its high viscosity. Gum tragacanth moisture content is 10-12 %.