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Guar gum, also called guaran, is a galactomannan. It is primarily the ground endosperm of guar beans. The guar seeds are dehusked, milled and screened to obtain the guar gum . It is typically produced as a free flowing, pale, off-white colored, coarse to fine ground powder.
Additional recommended knowledge
Guar gum is extracted from the guar bean, where it acts as a food and water store. The guar bean is principally grown in India and Pakistan, with smaller crops grown in the U.S.A., Australia and Africa. The drought-resistant guar bean can be eaten as a green bean, fed to cattle, or used in green manure, as seen on "dirt jobs". Moreover China also started growing the crop of Guar.
Solubility and Viscosity
Guar gum is more soluble than locust bean gum and is a better emulsifier as it has more galactose branch points. Unlike locust bean gum, it is not self-gelling. However, either borax or calcium can cross-link guar gum, causing it to gel. In water it is nonionic and hydrocolloidal. It is not affected by ionic strength or pH, but will degrade at pH extremes at temperature (e.g. pH 3 at 50°C). It remains stable in solution over pH range 5-7. Strong acids cause hydrolysis and loss of viscosity, and alkalies in strong concentration also tend to reduce viscosity. It is insoluble in most hydrocarbon solvents.
Guar gum shows high low-shear viscosity but is strongly shear-thinning. It is very thixotropic above concentration 1%, but below 0.3% the thixotropy is slight. It has much greater low-shear viscosity than that of locust bean gum, and also generally greater than that of other hydrocolloids. Guar Gum shows viscosity synergy with xanthan gum. Guar gum and micellar casein mixtures can be slightly thixotropic if a biphase system forms.
Guar gum is economical because it has almost 8 times the water-thickening potency of cornstarch - only a very small quantity is needed for producing sufficient viscosity. Thus it can be used in various multi-phase formulations; as an emulsifier because it helps to prevent oil droplets from coalescing, and/or as a stabilizer because it helps to prevent solid particles from settling.
Guar gum retards ice crystal growth non-specifically by slowing mass transfer across the solid/liquid interface. It shows good stability during freeze-thaw cycles.
Manufacturers define different grades and qualities of guar gum by the particle size, the viscosity that is generated with a given concentration, and the rate at which that viscosity develops. Coarse-mesh guar gums, will typically -- but not always -- develop viscosity more slowly. They may achieve a reasonably high viscosity, but will take longer to achieve. On the other hand, they will disperse better than fine-mesh, all conditions being equal. A finer mesh, like a 200 mesh, requires more effort to dissolve .
The largest market for guar gum is in the food industry. It is generally recognized as safe (GRAS) in the US with differing percentages set for its allowable concentration in various food applications. In Europe, guar gum has EU food additive code E412.
Nutritional and medicinal effects
Guar gum is a water-soluble fiber that acts as a bulk forming laxative, and as such, it is claimed to be effective in promoting regular bowel movements and relieve constipation and chronic related functional bowel ailments; such as diverticulosis, Crohn's disease, colitis and irritable bowel syndrome, among others. The increased mass in the intestines stimulates the movement of waste and toxins from the system, which is particularly helpful for good colon health, because it speeds the removal of waste and bacteria from the bowel and colon. In addition, because it is soluble, it is also able to absorb toxic substances (bacteria) that cause infective diarrhea.
Several studies have found significant decreases in human serum cholesterol levels following guar gum ingestion. These decreases are thought to be a function of its high soluble fiber content.
Guar gum is of interest with regards to both weight loss and diabetic diets. It is a thermogenic substance. Moreover, its low digestibility lends its use in recipes as a filler, which can help to provide satiety, or slow the digestion of a meal, thus lowering the glycemic index of that meal. In the late 1980s, guar gum was used and heavily promoted in several weight loss products. The USFDA eventually recalled these due to reports of esophageal blockage from insufficient fluid intake. For this reason, guar gum is no longer approved for use in over-the-counter weight loss aids in the United States. Moreover, a meta-analysis that combined the results of 11 randomized controlled trials found that guar gum supplements were not effective in reducing body weight.
Two Japanese studies using rats showed that guar gum supports increased absorption of calcium occurring in the colon instead of in the small intestine. This means that lesser amounts of calcium may be consumed in order to obtain its recommended minimum daily intake (RDI). This has obvious implications for reduced calorie diets, since calcium rich dairy products tend to be high in calories.
However, guar gum is also capable of reducing the absorbability of dietary minerals (other than calcium), when foods and/or nutritional supplements containing them are consumed concomitantly with it. However, this is less of a concern with guar gum than with various nonsoluble dietary fibers.
Some studies have found guar gum to improve dietary glucose tolerance. Research has revealed that the water soluble fiber in it may help people with diabetes by binding with glucose in the gastrointestinal tract, thus preventing its absorption.
It also functions as an adjuvant for diabetic drugs that are sometimes employed for the treatment of noninsulin dependent diabetes. The effect is to help lower blood glucose levels. Thus, diabetic patients who are taking drugs should consult their doctors before supplementing with guar gum.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Guar_gum". A list of authors is available in Wikipedia.|