Guar gum

Guar gum usp nf
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.