Guar gum

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, off-white powder.

Production and trade

The guar bean is principally grown in India, Pakistan, US, China, Australia and Africa. India produces 2.5 - 3.5 million tons of guar annually, making it the largest producer with about 80% of world production.

In India, Rajasthan, Gujarat and Haryana are the main producing regions, and Jodhpur, Sri Ganganagar and Hanumangarh in Rajasthan are the major Guar trading markets. Hanumangarh - Ganganagar is the main production area for best quality guar beans, so called "Fast-Hydrating Guar".

The United States has produced 4,600 to 14,000 tonnes of guar over the last 5 years. 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 1.0 Million tonnes. Industrial guar gum accounts for about 70% of the total demand. Mainly it is used as a proppant transport / proppant suspending agent in Hydraulic Fracturing Process. 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. 2013 was a strong year for guar sowing and production in India.In 2013 the export of Guar and Guar Gum was so strong that this humble cash crop of India topped the agro export commodity list of INDIA. The total sowing area rose by 21 percent in 2013 to reach 10.6 million acres. Rajasthan, Haryana, and Gujarat â€" the three key guar-producing states â€" exceeded the sowing area target set by their respective agriculture departments. Non-traditional guar cultivators in other Indian states also showed keen interest in the crop in 2013.

Properties

Chemical composition

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

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. 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 extreme pH and 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 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.

Thickening

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

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

Grading

Guar gum is analysed for

Guar gum powder standards are:

• HS-Code- 130 232 30
• CAS No.- 9000-30-0
• EEC No.- E 412
• BT No.- 1302 3290
• EINECS No. - 232-536-8
• Imco Code- Harmless

Manufacturing process

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.

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.

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

Industrial applications

• Textile industry â€" sizing, finishing and printing
• Paper industry â€" improved sheet formation, folding and denser surface for printing
• Explosives industry â€" as waterproofing agent mixed with ammonium nitrate, nitroglycerin, etc.
• Pharmaceutical industry â€" as binder or as disintegrator in tablets; main ingredient in some bulk-forming laxatives
• Cosmetics and toiletries industries â€" thickener in toothpastes, conditioner in shampoos (usually in a chemically modified version)
• Hydraulic fracturing Shale oil and gas extraction industries consumes about 90% of guar gum produced from India and Pakistan.
• Mining
• Hydroseeding â€" formation of seed-bearing "guar tack"
• Medical institutions, especially nursing homes - used to thicken liquids and foods for patients with dysphagia
• Fire retardant industry - as a thickener in Phos-Chek
• Nanoparticles industry - to produce silver or gold nanoparticles, or develop innovative medicine delivery mechanisms for drugs in pharmaceutical industry.

Food applications

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. 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:

• In baked goods, it increases dough yield, gives greater resiliency, and improves texture and shelf life; in pastry fillings, it prevents "weeping" (syneresis) of the water in the filling, keeping the pastry crust crisp. It is primarily used in hypoallergenic recipes that use different types of whole-grain flours. Because the consistency of these flours allows the escape of gas released by leavening, guar gum is needed to improve the thickness of these flours, allowing them to rise as a normal flour would.
• In dairy products, it thickens milk, yogurt, kefir, and liquid cheese products, and helps maintain homogeneity and texture of ice creams and sherbets. It is used for similar purposes in plant milks.
• For meat, it functions as a binder.
• In condiments, it improves the stability and appearance of salad dressings, barbecue sauces, relishes, ketchups and others.
• In canned soup, it is used as a thickener and stabilizer.
• It is also used in dry soups, instant oatmeal, sweet desserts, canned fish in sauce, frozen food items, and animal feed.

Nutritional and medicinal effects

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.

Guar gum has been considered of interest in regard 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 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. 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.

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.

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. 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

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.

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.

Dioxin contamination

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. PCP contains dioxins as contamination. Dioxins damage the human immune system.

References