Guar gum

• BPGuar Galactomannan
• Ph. Eur.Guar Galactomannan
• USP–NFGuar Gum

Galactosol; guar flour; guar galactomannan; jaguar gum; Meyprogat; E412

Galactomannan polysaccharide: a (1→4)-linked β-D-mannopyranose backbone with single (1→6)-linked α-D-galactopyranose side chains (mannose:galactose about 2:1) · [9000-30-0]

(C6H12O6)n · ≈ 220 000

Gelling agent, viscosity modifier, Binder

Typical concentrations: — · Dosage forms: Liquid, Solid

Used in oral and topical products as a suspending, thickening and stabilising agent, and in tablets as a binder and disintegrant. Typical concentrations: emulsion stabiliser about 1%; thickener for lotions and creams up to 2.5%; tablet binder up to 10%. It has also been studied as a matrix former for sustained release and as a carrier for colon-targeted delivery, since it is degraded by colonic bacteria. It is widely used in foods.

A white to yellowish-white, almost odourless powder with a bland taste. It disperses in cold or hot water and hydrates to form a highly viscous, slightly cloudy colloidal dispersion.

Viscosity

high at 1% w/v; develops over a period of hours as the gum hydrates and depends on grade and particle size

pH

5.0–7.0 (1% w/v aqueous dispersion)

Moisture content

up to about 15% w/w

Solubility

practically insoluble in ethanol and other organic solvents; dispersible and swells in water

Ionic character

non-ionic; viscosity is little affected by pH between about 4 and 10.5

The powder is stable in a well-closed container in a cool, dry place. Aqueous dispersions are sensitive to microbial and enzymatic degradation and need a preservative; viscosity falls on prolonged heating and at extremes of pH.

Borate ions cross-link guar gum and cause gelation. It is incompatible with acetone, tannins and strong acids and alkalis, and high concentrations of ethanol or salts reduce hydration and viscosity.

Obtained from the ground endosperm of the seeds of the guar plant, Cyamopsis tetragonolobus (Leguminosae). The seed husk and germ are removed and the endosperm is milled and sieved.

Generally regarded as non-toxic and non-irritant; it is not digested in the small intestine. Large oral amounts can cause flatulence, diarrhoea and nausea. Tablets of guar gum taken as a dietary fibre have caused oesophageal and intestinal obstruction when swallowed with too little water. It can lower post-prandial blood glucose and reduce the absorption of some drugs.

Observe normal precautions for the quantity handled. Guar gum dust may be irritant and is a recognised cause of occupational asthma; use eye protection, gloves and a dust respirator.

GRAS listed. Accepted as a food additive in Europe (E412). Included in the FDA Inactive Ingredient Database (oral tablets and suspensions; topical preparations) and in non-parenteral medicines licensed in Europe.

Ceratonia (locust bean gum); hydroxypropyl guar; tara gum; xanthan gum.

To avoid lumps, sprinkle the powder slowly into vigorously stirred water or pre-disperse it in a non-solvent such as glycerin or ethanol. Mixtures of guar gum with xanthan gum show synergistic increases in viscosity.