Guar Gum is a gum obtained from the ground endosperms of Cyamopsis tetragonolobus (Linn) Taub. (Fam. Leguminosae). It consists chiefly of a high molecular weight hydrocolloidal polysaccharide, composed of galactan and mannan units combined through glycosidic linkages, which may be described chemically as a galactomannan.
Identification:
A: Place about 2 g in a 400-mL beaker, moisten it with about 4 mL of isopropyl alcohol, add 200 mL of cold water with vigorous stirring, and continue stirring until the gum is completely and uniformly dispersed: an opalescent, viscous solution results.
B: Place about 100 mL of the solution prepared in Identification test A in a 400-mL beaker, heat in a boiling water bath for about 10 minutes, and cool: no appreciable increase in viscosity is produced (distinction from locust bean gum).
Tests:
Loss on drying: Dry it at 105 for 5 hours: it loses not more than 15.0% of its weight.
Total ash: not more than 1.5% of ash.
Acid-insoluble matter: Transfer about 1.5 g of Guar Gum, accurately weighed, to a 250-mL beaker containing 150 mL of water and 1.5 mL of sulfuric acid. Cover the beaker with a watch glass, and heat the mixture on a steam bath for 6 hours, rubbing down the wall of the beaker frequently with a rubber-tipped stirring rod, and replacing any water lost by evaporation. At the end of the 6-hour heating period add about 500 mg of a suitable filter aid, accurately weighed, and filter through a suitable tared, ashless filter. Wash the residue several times with hot water, dry the filter and its contents at 105 for 3 hours, cool in a desiccator, and weigh: the amount of acid-insoluble matter, determined by subtracting the weight of filter aid from that of the residue, is not more than 7.0% of the Guar Gum taken.
Arsenic: 3 ppm.
Lead: the limit is 0.001%.
Heavy metals: 0.002%.
Protein: not more than 10.0% of the Guar Gum taken.
Starch: To a 1 in 10 solution of Guar Gum add a few drops of iodine TS: no blue color is produced.
Content of galactomannans: Subtract from 100.0 the total percentages of Loss on drying, Total ash, Acid-insoluble matter, and Protein: the content of galactomannans is not less than 66.0%.
INS: 412 CAS: [9000-30-0]
DESCRIPTION
Guar Gum occurs as a white to yellow-white powder. It is a gum obtained from the ground endosperms of Cyamopsis tetragonolobus (L.) Taub (Fam. Leguminosae) (synonym Cyamopsis psoraloides [Lam.] D.C.). It consists chiefly of a high-molecular-weight polysaccharide composed of galactose and mannose units and may be described chemically as a galactomannan. It is dispersible in either hot or cold water, forming a sol, having a pH between 5.4 and 7.0, that may be converted to a gel by the addition of small amounts of sodium borate.
Function: Stabilizer; thickener; emulsifier.
REQUIREMENTS
Identification
A. Transfer a 2-g sample into a 400-mL beaker, moisten it thoroughly with about 4 mL of isopropyl alcohol, add, with vigorous stirring, 200 mL of cold water, and continue to stir until the gum is completely and uniformly dispersed. An opalescent, viscous dispersion forms.
B. Transfer 100 mL of the dispersion prepared in Identification Test A into another 400-mL beaker, heat the mixture in a boiling water bath for about 10 min, and then cool to room temperature. No appreciable increase in viscosity develops.
Acid-Insoluble Matter: Not more than 7.0%.
Ash: (Total) Not more than 1.5%.
Galactomannans: Not less than 70.0%.
Lead: Not more than 2 mg/kg.
Loss on Drying: Not more than 15.0%.
Protein: Not more than 10.0%.
Starch: Passes test.
