Guar gum

Description

Background. Guar gum, like locust bean gum, is a galactomannan derived from the seed of a leguminous plant. The source of guar, Cyamopsis tetragonolobus, is widely grown in Pakistan and India as cattle feed, and was introduced to the United States as a cover crop in 1903. The U.S. is now also a producer. It was not until 1953, however, that guar gum was produced on a commercial scale, primarily as a replacement for locus bean gum in the paper, textile and food industries. The most important property of guar is the ability to hydrate rapidly in cold water to attain a very high viscosity. In addition to the food industry, guar is used in the mining, paper, textile, ceramic, paint, cosmetic, pharmaceutical, explosive, and other industries.
Sources, Harvesting, and Producing Areas. The guar is a hardy and drought-resistant plant which grows three to six feet high with vertical stalks. The guar pods, which grow in clusters along the vertical stems, are about six inches long and contain 6 to 9 seeds, which are considerably smaller than locus bean seeds. As in the case of locust bean gum, the endosperm, which comprises 35-42%.

Chemical properties

Yellowish-white free-flowing powder. Completely soluble in hot or cold water. Practically insoluble in oils, greases, hydrocarbons, ketones, esters. Water solutions are tasteless, odorless, nontoxic. Has 5-8 times the thickening power of starch. Reduces the friction drag of water on metals.

Chemical properties

The USP32–NF27 describes guar gum as a gum obtained from the ground endosperms of Cyamopsis tetragonolobus (L.) Taub. (Fam. Leguminosae). It consists chiefly of a high-molecular-weight hydrocolloidal polysaccharide, composed of galactan and mannan units combined through glycoside linkages, which may be described chemically as a galactomannan. The PhEur 6.3 similarly describes guar galactomannan as being obtained from the seeds of Cyamopsis tetragonolobus (L.) Taub. by grinding the endosperms and subsequent partial hydrolysis.
The main components are polysaccharides composed of Dgalactose and D-mannose in molecular ratios of 1 : 1.4 to 1 : 2. The molecule consists of a linear chain of b-(1!4)-glycosidically linked manno-pyranoses and single a-(1→6)-glycosidically linked galactopyranoses.
Guar gum occurs as an odorless or nearly odorless, white to yellowish-white powder with a bland taste.

Chemical properties

Guar gum is the endosperm of the seed of the Indian cluster bean, Cyamopsis tetragonolobus. It has been grown for several thousand years in India and Pakistan as a vegetable and a forage crop. The guar is a hardy and drought-resistant plant, which grows 1 to 2 m high with vertical stalks and resembles the soybean plant in general appearance. The guar pods, which grow in clusters along the vertical stems, are about 30 cm long and contain six to nine seeds, which are considerably smaller than locust bean seeds Guar gum is odorless. As in the case of locust bean gum, the endosperm, which comprises 35 to 42% of the seed, is the source of the gum Typically, guar gum is around 80% of the endosperm of the guar seed. As the endosperm is about 40% of the seed, guar gum is roughly 30% of the guar plant seed. It is harvested before the frst rain following the frst frost to obtain maximum yield and purity (Burdock, 1997).

Physical properties

Guar gum is a white to yellowish-white powder It is dispersible in either hot or cold water, forming a solution having a pH between 5.4 and 7.0 that may be converted to gel by the addition of a small amount of sodium borate.

Occurrence

Guar gum is an annual found in India, the United States, and the tropics of Asia.

The Uses of Guar gum

Guar gum is obtained from the seed kernel of the plant cyamopsis tetragonoloba. It has a mannose:galactose ratio of approximately 2:1. It is dispersible in cold water to form viscous sols which upon heating will develop additional viscosity. A 1% solution has a viscosity range of 2,000–3,500 cp at 25°c. It is a versatile thickener and stabilizer used in ice cream, baked goods, sauces, and beverages at use levels ranging from 0.1 to 1.0%. It is scientifically termed guaran.

The Uses of Guar gum

low calorie, soluble dietery fiber

The Uses of Guar gum

In paper sizing; as a protective colloid, stabilizer, thickening and film forming agent for cheese, salad dressings, ice cream, soups; as a binding and disintegrating agent in tablet formulations; in pharmaceutical jelly formulations; in suspensions, emulsions, lotions, creams, toothpastes; in the mining industry as a flocculant, as a filtering agent; in water treatment as a coagulant aid.
Food additives, emulsifying stabilizer, thickener and gelling agent.

The Uses of Guar gum

guar gum has a coating action on the skin that allows for moisture retention. often used as a thickener and emulsifier in cosmetic formulations, guar gum is a polysaccharide found in the seeds of the guar plant. It is the nutrient material required by the developing plant embryo during germination. When the endosperm, once separated from the hull and embryo, is ground to a powder form, it is marketed as guar gum.

Definition

A water-soluble plant mucilage obtained from the ground endosperms of Cyanopsis tetragonoloba, cultivated in India and Pakistan as livestock feed, as well as in southwestern U.S. The water-soluble portion of the flour (85%) is called guaran and consists o

Production Methods

Guar gum is obtained from the ground endosperm of the guar plant, Cyamopsis tetragonolobus (L.) Taub. (Fam. Leguminosae), which is grown in India, Pakistan, and the semiarid southwestern region of the USA.
The seed hull can be removed by grinding, after soaking in sulfuric acid or water, or by charring. The embryo (germ) is removed by differential grinding, since each component possesses a different hardness. The separated endosperm, containing 80% galactomannan is then ground to different particle sizes depending upon final application.

General Description

Off-white to yellowish-white powder. Five to eight times the thickening power of starch. Water solutions are tasteless, odorless, and nontoxic and have a pale translucent gray color with neutral pH. Water solutions converted to gel by small amounts of borax.

Air & Water Reactions

The organic dusts can react violently when suspended in air in the presence of an ignitable source. . Insoluble in water.

Reactivity Profile

Guar gum is a ether-alcohol derivative, the ether being relatively unreactive. Flammable and/or toxic gases are generated by the combination of alcohols with alkali metals, nitrides, and strong reducing agents. They react with oxoacids and carboxylic acids to form esters plus water. Oxidizing agents convert alcohols to aldehydes or ketones. Alcohols exhibit both weak acid and weak base behavior. They may initiate the polymerization of isocyanates and epoxides.

Health Hazard

ACUTE/CHRONIC HAZARDS: When heated to decomposition Guar gum emits irritating fumes and smoke.

Fire Hazard

Flash point data for Guar gum are not available. However, Guar gum is probably combustible.

Pharmaceutical Applications

Guar gum is a galactomannan, commonly used in cosmetics, food products, and pharmaceutical formulations. It has also been investigated in the preparation of sustained-release matrix tablets in the place of cellulose derivatives such as methylcellulose.
In pharmaceuticals, guar gum is used in solid-dosage forms as a binder and disintegrant; in oral and topical products as a suspending, thickening, and stabilizing agent; and also as a controlled-release carrier. Guar gum has also been examined for use in colonic drug delivery. Guar-gum-based three-layer matrix tablets have been used experimentally in oral controlled-release formulations.
Therapeutically, guar gum has been used as part of the diet of patients with diabetes mellitus. It has also been used as an appetite suppressant, although its use for this purpose, in tablet form, is now banned in the UK.

Biochem/physiol Actions

Guar gum has been shown to have numerous beneficial effects including improved glucose tolerance and attenuation of diabetic nephropathy.

Safety

Guar gum is widely used in foods, and oral and topical pharmaceutical formulations. Excessive consumption may cause gastrointestinal disturbance such as flatulence, diarrhea, or nausea. Therapeutically, daily oral doses of up to 25 g of guar gum have been administered to patients with diabetes mellitus.
Although it is generally regarded as a nontoxic and nonirritant material, the safety of guar gum when used as an appetite suppressant has been questioned. When consumed, the gum swells in the stomach to promote a feeling of fullness. However, it is claimed that premature swelling of guar gum tablets may occur and cause obstruction of, or damage to, the esophagus. Consequently, appetite suppressants containing guar gum in tablet form have been banned in the UK. However, appetite suppressants containing microgranules of guar gum are claimed to be safe. The use of guar gum for pharmaceutical purposes is unaffected by the ban.
In food applications, an acceptable daily intake of guar gum has not been specified by the WHO.
LD50 (hamster, oral): 6.0 g/kg
LD50 (mouse, oral): 8.1 g/kg
LD50 (rabbit, oral): 7.0 g/kg
LD50 (rat, oral): 6.77 g/kg

storage

Aqueous guar gum dispersions have a buffering action and are stable at pH 4.0–10.5. However, prolonged heating reduces the viscosity of dispersions.
The bacteriological stability of guar gum dispersions may be improved by the addition of a mixture of 0.15% methylparaben and 0.02% propylparaben as a preservative. In food applications, benzoic acid, citric acid, sodium benzoate, or sorbic acid may be used.
Guar gum powder should be stored in a well-closed container in a cool, dry place.

Properties and Applications

Items	Standard
Appearance	Light yellow free flow powder
120mesh residue	1% max
200mesh residue	10% max
Moisture	10% max
pH	6.5-7.5
Apparent viscosity (30oC,170s,0.6%)mpa.s	110 min
Water insolubles	4% max
Crosslinking property	Can be picked up by glass rod
Fluidity	Good
Hydroxypropyl degree of substitution	0.30 min

Incompatibilities

Guar gum is compatible with most other plant hydrocolloids such as tragacanth. It is incompatible with acetone, ethanol (95%), tannins, strong acids, and alkalis. Borate ions, if present in the dispersing water, will prevent the hydration of guar gum. However, the addition of borate ions to hydrated guar gum produces cohesive structural gels and further hydration is then prevented. The gel formed can be liquefied by reducing the pH to below 7, or by heating.
Guar gum may reduce the absorption of penicillin V from some formulations by a quarter.

Regulatory Status

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral suspensions, syrups, and tablets; topical preparations; vaginal tablets). Also included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.