Guar Gum

GUAR GUM

Synonyms

Guar gum, Jaguar gum, Guar flour and Decorpa.

Biological Source

Guar gum is a seed gum produced from the powdered endosperm of the seeds of Cyamopsis tetragonolobus Linn belonging to family Leguminosae.

Geographical Source

Guar or cluster bean is a drought-tolerant annual legume that was introduced into the United States from India in 1903. Commercial production of guar in the United States began in the early 1950s and has been concentrated in northern Texas and south-western Oklahoma. The major world suppliers are India, Pakistan and the United States, Australia and Africa. Rajasthan in western India is the major guar-producing state, accounting for 70% of the production. Guar is also grown in Gujarat, Haryana, Punjab and in some parts of Uttar Pradesh and Madhya Pradesh. India grows over 850,000 tons, or 80% of the total guar produced all over the world. 75% of the guar gum or derivatives produced in India are exported, mainly to the United States and to European countries.

Cultivation, Collection and Preparation

The plant of gaur gum is draught resistance and quite hardy in its constitutions. It is generally shown in May– June and harvested in September–October. At the stage of full maturity, the plant yields 600–800 lb of seeds per acre under un-irrigated conditions but the production nearly doubles under irrigated conditions.

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 the endosperm 35–40%, germ (or embryo) 45–50% and husk 14–17%.

The cotyledons, having a distinct bitter taste are separated from the endosperm by the process called ‘winnowing’. The crude guar gum, that is, the endosperms is subsequently pulverized by means a ‘micro-pulverizer’ 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 pulver-ized and shifted for several hours till a final white powder or granular product is obtained.

Morphology

                               Cyamopsis tetragonolobus

History

Guar gum is a dietary fibre obtained from the endosperm of the Indian cluster bean. The endosperm can account for more than 40% of the seed weight and is separated and ground to form commercial guar gum.

Guar gum has been used for centuries as a thickening agent for foods and pharmaceuticals. It continues to find extensive use for these applications and also is used by the paper, textile and oil-drilling industries.

Chemical Constituents

The water-soluble part of guar gum contains mainly of a high molecular weight hydrocolloidal polysaccharide, that is, galactomannan, which is commonly known as guaran. Guaran 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. The gum also contains about 5–7% of proteins.

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).

5.     Aqueous solution of guar gum is converted to a gel by addition of a small amount of borax.

Uses

Guar gum is used as a protective colloid, a binding and disintegrating agent, emulsifying agent, bulk laxative, appe-tite depressant and in peptic ulcer therapy. Industrially, it is used in paper manufacturing, printing, polishing, textiles and also in food and cosmetic industries. Guar gum is extensively used as flocculent in ore-dressing and treat-ment of water.

Guar gum has been shown to decrease serum total cho-lesterol levels by about 10–15% and low-density lipoprotein cholesterol (LDL-cholesterol) by up to 25% without any significant effect on triglycerides or high-density lipoprotein cholesterol (HDL-cholesterol) levels.

The ability of guar to affect gastrointestinal transit may contribute to its hypoglycemic activity. Guar reduces postprandial glucose and insulin levels in both healthy and diabetic subjects and may be a useful adjunct in the treatment of noninsulin-dependent diabetes.

Guar gum remains important ingredient in over-the-counter weight loss preparations. Even in the absence of weight loss, guar supplementation for 2 weeks reduced blood pressure by 9% in moderately overweight men.

Toxicology

In the colon, guar gum is fermented to short-chain fatty acids. Both guar and its resultant by-products do not appear to be absorbed by the gut. The most common adverse effects, therefore, are gastrointestinal, including gastrointestinal pain, nausea, diarrhoea and flatulence. Approximately half of those taking guar experience flatulence; this usually occurs early in treatment and resolves with continued use. Starting with doses of about 3 g three times a day, not to exceed 15 g per day, can minimize gastrointestinal effects.

Guar gum may affect the absorption of concomitantly administered drugs. Bezafibrate, acetaminophen (e.g. Tylenol), digoxin (e.g. Lanoxin), glipizide (e.g. Glucotrol) or glyburide (e.g. DiaBeta, Micronase) are generally unaf-fected by concomitant administration. The ingestion of more than 30 g of guar per day by diabetic patients did not adversely affect mineral balances after six months. Guar gum in a weight-loss product has been implicated in esophageal obstruction in a patient who exceeded the recommended dosage. In a recent review, 18 cases of esophageal obstruc-tion, seven cases of small bowel obstruction, and possibly one death were associated with the use of Cal-Ban 3000, a guar gum containing diet pill. The water-retaining capacity of the gum permits it to swell to 10- to 20-fold and may lead to luminal obstruction, particularly when an anatomic predisposition exists. Guar always should be taken with large amounts of liquid. Occupational asthma has been observed among those working with guar gum. Because of its potential to affect glycemic control, guar gum should be used cautiously by diabetic patients.

Marketed Product

Ascenta Omega Smooth Orange Sensation by Ascenta Health Ltd.