Guar gum

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Guar gum
Identifiers
CAS number9000-30-0 YesY
ATC codeA10BX01
Properties
Acidity (pKa)5-7
Hazards
MSDSMSDS
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references
 
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Guar gum
Identifiers
CAS number9000-30-0 YesY
ATC codeA10BX01
Properties
Acidity (pKa)5-7
Hazards
MSDSMSDS
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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.[1] It is typically produced as a free-flowing, off-white powder.

Production and trade[edit]

The guar bean is principally grown in India and Australia, with smaller crops in the US, China, Pakistan and Africa. In India, Rajasthan, Gujarat and Haryana are the main producing regions, and Churu, Jodhpur, Sri GangaNagar and Hanumangarh in Rajasthan are the major Guar trading markets.

India produces 1 - 1.25 million tonnes of guar annually, making it the largest producer with about 80% of world production. In India, Punjab is the main production area for guar beans.

The United States has produced 4,600 to 14,000 tons of guar over the last 5 years.[2] As many as 50,000 acres of guar have been grown in West Texas over the last 50 years.

The world production for guar gum and its derivatives is about 700,000 tonnes. Industrial guar gum accounts for about 45% of the total demand. It is used as a controlling agent in oil wells to facilitate easy drilling and prevent fluid loss. In 2012 guar prices increased by 900-1000%. The main reason for this large scale price rise was the inventory build up by companies like Halliburton and Schlumberger, amidst the fear of shortage of guar gum for drilling due to ongoing drought in Rajasthan.

Properties[edit]

Chemical composition[edit]

Guaran.svg

Chemically, guar gum is a polysaccharide composed of the sugars galactose and mannose. The backbone is a linear chain of β 1,4-linked mannose residues to which galactose residues are 1,6-linked at every second mannose, forming short side-branches.

Solubility and viscosity[edit]

Guar gum is more soluble than locust bean gum and is a better stabilizer, as it has more galactose branch points. Unlike locust bean gum, it is not self-gelling.[3] 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).[3] 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 1% concentration, 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.[3][4]

Thickening[edit]

Guar gum is economical because it has almost eight 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 multiphase 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.

Ice crystal growth[edit]

Guar gum retards ice crystal growth nonspecifically by slowing mass transfer across the solid/liquid interface. It shows good stability during freeze-thaw cycles.[3]

Grading[edit]

Guar gum is analysed for

TestTest MethodTestTest method
ColourTP/09Acid-insoluble residueTP/115
ViscosityTP/10/04Fat contentTP/18
Granulation (mesh)TP/21Ash contentTP/12
Moisture, pHTP/1 and TP/29Gum contentTP/03
ProteinTP/05Heavy metalsTP/13
Insolubles AshTP/11FilterabilityTP/20A

Guar gum powder standards are:

Manufacturing process[edit]

Depending upon the requirement of end product, various processing techniques are used. The commercial production of guar gum normally uses roasting, differential attrition, sieving, and polishing.

Food-grade guar gum is manufactured in stages. Guar split selection is important in this process. The split is screened to clean it and then soaked to prehydrate it in a double-cone mixer. The prehydrating stage is very important because it determines the rate of hydration of the final product.

The soaked splits, which have reasonably high moisture content, are passed through a flaker. The flaked guar split is ground and then dried. The powder is screened through rotary screens to deliver the required particle size. Oversize particles are either recycled to main ultra fine or reground in a separate regrind plant, according to the viscosity requirement.

This stage helps to reduce the load at the grinder. The soaked splits are difficult to grind. Direct grinding of those generates more heat in the grinder, which is not desired in the process, as it reduces the hydration of the product. Through the heating, grinding, and polishing process, the husk is separated from the endosperm halves and the refined guar split is obtained. Through the further grinding process, the refined guar split is then treated and converted into powder.

The split manufacturing process yields husk and germ called “guar meal”, widely sold in the international market as cattle feed. It is high in protein and contains oil and albuminoids, about 50% in germ and about 25% in husks. The quality of the food-grade guar gum powder is defined from its particle size, rate of hydration, and microbial content. E412 guar gum is an important natural food supplement with high nutritional value.[citation needed]

Manufacturers define different grades and qualities of guar gum by the particle size, the viscosity 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, such as a 200 mesh, requires more effort to dissolve.[5]

Modified forms of guar gum are available commercially, including enzyme-modified, cationic and hydropropyl guar.[6]

Industrial applications[edit]

Food applications[edit]

The largest market for guar gum is in the food industry. In the US, differing percentages are set for its allowable concentration in various food applications.[9] In Europe, guar gum has EU food additive code E412. Xanthan gum and guar gum are the most frequently used gums in gluten-free recipes and gluten-free products.

Applications include:

Nutritional and medicinal effects[edit]

Guar gum, as a water-soluble fiber, acts as a bulk-forming laxative, so is claimed to be effective in promoting regular bowel movements and relieving constipation and chronic related functional bowel ailments, such as diverticulosis, Crohn's disease, colitis and irritable bowel syndrome.

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.[citation needed]

Guar gum has been considered of interest in regard to both weight loss and diabetic diets. It is a thermogenic substance.[11] 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 US Food and Drug Administration eventually recalled these due to reports of esophageal blockage from insufficient fluid intake, after one brand alone caused at least 10 users to be hospitalized, and a death.[12] 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 combining the results of 11 randomized, controlled trials found guar gum supplements were not effective in reducing body weight.[13]

Two Japanese studies using rats showed guar gum supports increased absorption of calcium occurring in the colon instead of in the small intestine. This means lesser amounts of calcium may be consumed to obtain its recommended minimum daily intake. This has obvious implications for reduced calorie diets, since some calcium-rich dairy products tend to be high in calories.[citation needed]

Guar gum, though, is also capable of reducing the absorbability of dietary minerals (other than calcium), when foods or nutritional supplements containing them are consumed concomitantly with it, but this is less of a concern with guar gum than with various insoluble dietary fibers.

Some studies have found guar gum to improve dietary glucose tolerance.[14] Research has revealed the water-soluble fiber in it may help people with diabetes by slowing the absorption of sugars by the small intestine. Although the rate of absorption is reduced, the amount of sugar absorbed is the same overall. This may help diabetic patients by moderating glucose "spikes".

Allergies[edit]

Some studies have found an allergic sensitivity to guar gum developed in a few individuals working in an industrial environment where airborne concentrations of the substance were present. In those affected by the inhalation of the airborne particles, common adverse reactions were occupational rhinitis and asthma.[15]

Soy protein occurs as an impurity in manufactured guar gum, and can make up as much as 10%. The guar gum can therefore adversely affect those with sensitivity to soy.[16]

Dioxin contamination[edit]

In July 2007, the European Commission issued a health warning to its member states after high levels of dioxins were detected in a food additive - guar gum - used as thickener in small quantities in meat, dairy, dessert or delicatessen products. The source was traced to guar gum from India that was contaminated with pentachlorophenol, a pesticide no longer in use.[17] PCP contains dioxins as contamination. Dioxins damage the human immune system.[18]

References[edit]

  1. ^ "foa.org" (PDF). Retrieved 2011-04-18. 
  2. ^ Guar in West Texas http://lubbock.tamu.edu/files/2013/06/Guar-Production-Industry-Texas-May2013-Trostle.pdf
  3. ^ a b c d Martin Chaplin "Water Structure and Behavior: Guar Gum". April 2012. London South Bank University
  4. ^ Lynn A. Kuntz. "Special Effects With Gums". December 1999. Food Product Design
  5. ^ foodproductdesign.com
  6. ^ Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, page 4770
  7. ^ Ram Narayan (August 8, 2012). "From Food to Fracking: Guar Gum and International Regulation". RegBlog. University of Pennsylvania Law School. Retrieved 15 August 2012. 
  8. ^ "Product description: Guar Tack. S&S Seeds Inc. 2006". Ssseeds.com. Retrieved 2011-04-18. 
  9. ^ fda.gov- Food additive list
    Maximum Usage Levels Permitted- Guar gum
  10. ^ Source: NOW Foods. Guar Gum Nutrition Label. Bloomingdale, IL: n.p., n.d.
  11. ^ JC Brown & G Livesey. "Energy balance and expenditure while consuming guar gum at various fat intakes and ambient temperatures". Am J Clin Nutr. 1994. 60(6):956-64 (ISSN: 0002-9165)
  12. ^ Dietary Supplements: Making Sure Hype Doesn't Overwhelm Science (November 1993)
  13. ^ Pittler MH, "Ernst E. Guar gum for body weight reduction: meta-analysis of randomized trials". Am J Med. 2001;110(9):724-730.
  14. ^ Daumerie C, Henquin JC, "Acute effects of guar gum on glucose tolerance and intestinal absorption of nutrients in rats". Diabete Metab. 1982 Mar;8(1):1-5.
  15. ^ "AllergyNet - Allergy Advisor Find". Allallergy.net. Retrieved 2013-02-19. 
  16. ^ "Guar Gum And Soy Allergy". Livestrong.Com. Retrieved 2013-02-19. 
  17. ^ "Commission Regulation (EU) No 258/2010". 2010-03-25. Retrieved 2012-07-14. 
  18. ^ "Dioxins and their effects on human health". 2010-05-01. Retrieved 2012-02-08.