2.2.2.4 Guar Gum
Synonyms Guar flour; Decorpa; Jaguar; Gum cyamopsis; Cyamopsis gum; Burtonite V-7-E.
Biological Source Guar gum is the ground endosperms of Cyamopsis tetragonolobus (L.) Taub; belonging to family Leguminoseae.
Geographical Source It grows abundantly in tropical countries like: Indonesia, India, Pakistan and Africa. In USA, southern western regions it was introduced in the year 1900 and its large-scale production commenced in early 1950’s.
Preparation First of all the fully developed white seeds of Guar gum are collected and freed from any foreign substances. The sorted seeds are fed to a mechanical ‘splitter’ to obtain the bifurcated guar seeds which are then separated into husk and the respective cotyledons having the ‘embryo’. The gum is found into the endosperm. Generally, the guar seeds comprise of the following:
Endosperm : 35 to 40%
Germ (or Embryo) : 45 to 50%, and
Husk : 14 to 17%
The cotyledons, having a distinct bitter taste are separated from the endosperm by the process called ‘winnowing’. The crude guar gum i.e., the endosperms is subsequently pulverised by means of a ‘micro-pulveriser’ followed by grinding. The relatively softer cotyledons sticking to the endosperms are separated by mechanical ‘sifting’ process. Thus, the crude guar-gum is converted to a purified form (i.e., devoid of cotyledons), which is then repeatedly pulverized and shifted for several hours till a final white powder or gramular product is obtained.
Description
Colour : Colourless; Pale-yellowish white powder
Odour : Characteristic smell
Taste : Mucilagenous
Solubility : Insoluble in alcohol with water it gives a thick transparent suspension
Chemical Constituents It has been found that the water soluble fraction constitutes 85% of Guar gum and is commonly known as Guaran. It essentially consists of linear chains of (1 → 4) –β-D mannopyranosyl units with α–D-galactopyranosyl units attached by (1 → 6) linkages. However, the ratio of D-galactose to D-mannose is 1:2.
Chemical Tests
1. On being treated with iodine solution (0.1 N) it fails to give olive-green colouration.
2. It does not produce pink colour when treated with Ruthenium Red solution (distinction from sterculia gum and agar)
3. A 2% solution of lead acetate gives an instant white precipitate with guar gum (distinction from sterculia gum and acacia)
4. A solution of guar gum (0.25 g in 10 ml of water) when mixed with 0.5 ml of benzidine (1% in ethanol) and 0.5 ml of hydrogen peroxide produces no blue colouration (distinction from gum acacia).
Uses
1. It is used therapeutically as a bulk laxative.
2. It is employed as a protective colloid.
3. It is also used as a thickner and its thickening property is 5 to 8 times more than starch.
4. It finds its use in peptice ulcer therapy.
5. It is used as an anorectic substance i.e., it acts as an appetite depressant.
6. It is employed both as a binding and a disintegrating agent in tablet formulations.
7. It is used in paper sizing.
8. It is abundantly employed as film forming agent for cheese, salad dressing, ice-cream and soups.
9. It is used in pharmaceutical jelly formulations.
10. It is widely used in suspensions, emulsions, lotions, creams and toothpastes.
11. It is largely used in mining industry as a flocculant and also as a filtering agent.
12. It is also employed in water treatment plants as a coagulant aid.
