Guar gum, also called E412, has thickening and stabilizing properties useful in food, feed, and industrial applications.
Guar gum is a gel-forming galactomannan obtained by grinding the endosperm portion of Cyamopsis tetragonolobus, a leguminous plant grown for centuries mainly in India and Pakistan where it is a most important crop that has long been used as food for humans and animals
Guar gum is a novel agrochemical processed from endosperm of cluster bean.
GUAR GUM is mainly used powder as an additive in food, pharmaceuticals, paper, textile, explosive, oil well drilling and cosmetics industry. Industrial applications of guar gum are possible because of its ability to form hydrogen bonding with water molecule.
GUAR GUM is used as thickener and stabilizer in various industries including food, pharmaceuticals, paper, textile, explosive, oil well drilling and cosmetics industries.
CAS Number: 9000-30-0
E number: E412
EC / List no.: 232-536-8
SYNONYMS:
IUPAC names
(2S,5'R)-7-chloro-3',4,6-trimethoxy-5'-methylspiro[1-benzofuran-2,4'-cyclohex-2-ene]-1',3-dione
Cyamopsis gum; Cyanopsis tetragonoloba
disodium;[[[5-(6-aminopurin-9-yl)-3-hydroxyoxolan-2-yl]methoxy-hydroxyphosphoryl]oxy-oxidophosphoryl] hydrogen phosphate
galactomannan polysaccharide
GUAR GUM
Guar Hyroxypropyl Trimonium Chloride
The common names used in the scientific literature for the bean, guar gum flour and the galactomannan fraction are Indian cluster bean, guar and guaran, respectively.
Production and trade OF GUAR GUM
The guar bean is principally grown in India, Pakistan, the United States, Australia and Africa.
India is the largest producer, accounting for nearly 80% of the world production.
In India, Rajasthan, Gujarat, and Haryana are the main producing regions.
Properties of GUAR GUM
Chemical composition
Chemically, guar gum is an exo-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.
Guar gum has the ability to withstand temperatures of 80 °C (176 °F) for five minutes.
Solubility and viscosity
Guar gum is more soluble than locust bean gum due to its extra galactose branch points. Unlike locust bean gum, it is not self-gelling.
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.
The viscosity attained is dependent on time, temperature, concentration, pH, rate of agitation and particle size of the powdered gum used.
The lower the temperature, the lower the rate at which viscosity increases, and the lower the final viscosity. Above 80°, the final viscosity is slightly reduced.
Finer guar powders swell more rapidly than larger particle size coarse powdered gum.[citation needed][10]
Guar gum shows a clear low shear plateau on the flow curve and is strongly shear-thinning.
The rheology of guar gum is typical for a random coil polymer.
It does not show the very high low shear plateau viscosities seen with more rigid polymer chains such as xanthan gum.
It is very thixotropic above 1% concentration, but below 0.3%, the thixotropy is slight.
Guar gum shows viscosity synergy with xanthan gum. Guar gum and micellar casein mixtures can be slightly thixotropic if a biphase system forms.
Thickening
One use of guar gum is a thickening agent in foods and medicines for humans and animals.
Guar gum is also economical because it has almost eight times the water-thickening ability of other agents (e.g. cornstarch) and only a small quantity is needed for producing sufficient viscosity.
It forms breakable[clarification needed] gels when cross-linked with boron.
It is used in various multi-phase formulations for hydraulic fracturing, in some as an emulsifier because it helps prevent oil droplets from coalescing,and in others as a stabilizer to help prevent solid particles from settling and/or separating
Fracking entails the pumping of sand-laden fluids into an oil or natural gas reservoir at high pressure and flow rate. This cracks the reservoir rock and then props the cracks open.
Water alone is too thin to be effective at carrying proppant sand, so guar gum is one of the ingredients added to thicken the slurry mixture and improve its ability to carry proppant.
There are several properties which are important :
1. Thixotropic: the fluid should be thixotropic, meaning it should gel within a few hours.
2. Gelling and de-gelling: The desired viscosity changes over the course of a few hours.
When the fracking slurry is mixed, it needs to be thin enough to make it easier to pump.
Then as it flows down the pipe, the fluid needs to gel to support the proppant and flush it deep into the fractures.
After that process, the gel has to break down so that it is possible to recover the fracking fluid but leave the proppant behind.
This requires a chemical process which produces then breaks the gel cross-linking at a predictable rate.
Ice crystal growth
Guar gum retards ice crystal growth by slowing mass transfer across the solid/liquid interface.
It shows good stability during freeze-thaw cycles. Thus, it is used in egg-free ice cream.
Guar gum has synergistic effects with locust bean gum and sodium alginate.
May be synergistic with xanthan: together with xanthan gum, it produces a thicker product (0.5% guar gum / 0.35% xanthan gum), which is used in applications such as soups, which do not require clear results.
Guar gum is a hydrocolloid, hence is useful for making thick pastes without forming a gel, and for keeping water bound in a sauce or emulsion.
Guar gum can be used for thickening cold and hot liquids, to make hot gels, light foams and as an emulsion stabilizer.
Guar gum can be used for cottage cheeses, curds, yoghurt, sauces, soups and frozen desserts.
Guar gum is also a good source of fiber with 80% soluble dietary fiber on a dry weight basis.
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 pre-hydrate 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.
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.
Industrial applications of GUAR GUM
Textile industry – sizing, finishing and printing
Paper industry – improved sheet formation, folding and denser surface for printing
Explosives industry – as waterproofing agent mixed with ammonium nitrate, nitroglycerin, etc.
Pharmaceutical industry – as binder or as disintegrator in tablets; main ingredient in some bulk-forming laxatives
Cosmetics and toiletries industries – 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.[17]
Fracturing fluids normally consist of many additives that serve two main purposes, firstly to enhance fracture creation and proppant carrying capability and secondly to minimize formation damage.
Viscosifiers, such as polymers and crosslinking agents, temperature stabilizers, pH control agents, and fluid loss control materials are among the additives that assist fracture creation.
Formation damage is minimized by incorporating breakers, biocides, and surfactants.
More appropriate gelling agents are linear polysaccharides, such as guar gum, cellulose, and their derivatives.
Guar gums are preferred as thickeners for enhanced oil recovery (EOR).
Guar gum and its derivatives account for most of the gelled fracturing fluids.
Guar is more water-soluble than other gums, and it is also a better emulsifier, because it has more galactose branch points.
Guar gum shows high low-shear viscosity, but it is strongly shear-thinning.
Being non-ionic, it is not affected by ionic strength or pH but will degrade at low pH at moderate temperature (pH 3 at 50 °C).
Guar's derivatives demonstrate stability in high temperature and pH environments.
Guar use allows for achieving exceptionally high viscosities, which improves the ability of the fracturing liquid to transport proppant.
Guar hydrates fairly rapidly in cold water to give highly viscous pseudoplastic solutions of, generally, greater low-shear viscosity than other hydrocolloids.
The colloidal solids present in guar make fluids more efficient by creating less filter cake.
Proppant pack conductivity is maintained by utilizing a fluid that has excellent fluid loss control, such as the colloidal solids present in guar gum.
Guar has up to eight times the thickening power of starch.
Derivatization of guar gum leads to subtle changes in properties, such as decreased hydrogen bonding, increased solubility in water-alcohol mixture, and improved electrolyte compatibility.
These changes in properties result in increased use in different fields, like textile printing, explosives, and oil-water fracturing applications.
Crosslinking Guar
Guar molecules have a tendency to aggregate during the hydraulic fracturing process, mainly due to intermolecular hydrogen bonding.
These aggregates are detrimental to oil recovery because they clog the fractures, restricting the flow of oil. Cross-linking guar polymer chains prevents aggregation by forming metal – hydroxyl complexes.
The first crosslinked guar gels were developed in the late ‘60s.
Several metal additives have been used for crosslinking, among them are chromium, aluminium, antimony, zirconium, and the more commonly used, boron.
Boron, in the form of B(OH)4, reacts with the hydroxyl groups on the polymer in a two step process to link two polymer strands together to form bis-diol complexes.
1:1 1,2 diol complex and a 1:1 1,3 diol complex, place the negatively charged borate ion onto the polymer chain as a pendant group.
Boric acid itself does not apparently complex to the polymer so that all bound boron is negatively charged.
The primary form of crosslinking may be due to ionic association between the anionic borate complex and adsorbed cations on the second polymer chain.
The development of cross-linked gels was a major advance in fracturing fluid technology.
Viscosity is enhanced by tying together the low molecular weight strands, effectively yielding higher molecular weight strands and a rigid structure.
Cross-linking agents are added to linear polysaccharide slurries to provide higher proppant transport performance, relative to linear gels.
Lower concentrations of guar gelling agents are needed when linear guar chains are cross-linked.
It has been determined that reduced guar concentrations provide better and more complete breaks in a fracture.
The breakdown of cross-linked guar gel after the fracturing process restores formation permeability and allows increased production flow of petroleum products .
Mining
Hydroseeding – 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.
Slime (toy), based on guar gum crosslinked with sodium tetraborate.
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.
The FDA has banned guar gum as a weight loss pill due to reports of the substance swelling and obstructing the intestines and esophagus.
For Cattle Feed, as it enhances in the production of more milk as well as more percentage of fat in the milk.
Physico-chemical properties of GUAR GUM
The biological properties of guar galactomannan and other such polysaccharides are dependent on their behavior in an aqueous medium. Guar gum swells and or dissolves in polar solvent on dispersion and form strong hydrogen bonds. In nonpolar solvents it forms only weak hydrogen bonds. The rate of guar gum dissolution and viscosity development generally increases with decreasing particle size, decreasing pH and increasing temperature. Hydration rates are reduced in the presence of dissolved salts and other water-binding agents such as sucrose (Bemiller and Whistler 1993).
Rheology
Rheology is the study of flow and deformation of material when external force is applied. Guar gum in aqueous solutions shows pseudoplastic or shear-thinning behavior which means reduction in viscosity with increasing shear rate as shown by many high molecular weight polymers. This shear-thinning behavior of guar gum aqueous solution increases with polymer concentration and molecular weight. Guar gum aqueous solutions also do not show yield stress properties (Whistler and Hymowitz 1979). Aqueous solutions of guar gum at 1% concentration show a typical behavior of macromolecular biopolymer with dominating loss modulus (G″) over storage modulus (G′) in lower frequency range. However, in high frequency range storage modulus dominates the loss modulus (Shobha and Tharanathan 2009). With time guar gum aqueous solutions showed a decrease in storage modulus (G′) and loss modulus (G″) (Chenlo et al. 2010).
Viscosity
The most significant characteristic of guar gum is its ability to hydrate rapidly in cold water systems to give highly viscous solutions. Guar gum forms a viscous colloidal dispersion when completely hydrated which is a thixotropic rheological system. Dilute solution of less than 1% concentration of guar gum are less thixotropic than solutions of concentration of 1% or higher (Glicksman 1969). As like the other gums, viscosity of guar gum is dependent on time, temperature, concentration, pH, ionic strength and also on type of agitation. Schlakman and Bartilucci (1957) examined thirteen different commercial samples, and found great variation in the viscosity property, particle size and rate of hydration. A 1% aqueous dispersion of good quality guar gum may show a high viscosity value of 10000 cP (Parija et al. 2001).
Hydration rate
Rate of hydration of guar gum varies. Hydration of about 2 h is required in practical applications in order to reach maximum viscosity. Hydration rate largely depend on particle size of guar gum powder. Hence, for quick initial viscosity, very fine mesh guar gums are available (Glicksman 1969). However, a considerable time interval is still desired for maximum hydration and viscosity to be achieved.
Hydrogen bonding activity
Hydrogen bonding activity of guar gum is due to the presence of hydroxyl group in guar gum molecule. Guar gum shows hydrogen bonding with cellulosic material and hydrated minerals. With slight addition of guar gum, there is alteration in electrokinetic properties of any system markedly (Glicksman 1969). Substitution of hydroxyl groups in guar gum with hydroxypropyl causes steric hindrance that decreases the stability of hydrogen bonds (Cheng and Prud’homme 2002).
Factors affecting viscosity and hydration rate
Viscosity and hydration rate of guar gum does not remain constant but changes with conditions like temperature, pH, solute, concentration, etc.
Temperature
Temperature is the most significant factor that affects the rate of hydration and maximum viscosity. Guar solutions reach maximum viscosity much faster when prepared at higher temperatures than those at lower temperatures. But the prolonged heat is also considered to have degradative effect. In most of the cases, guar gum solutions prepared by heating have a lower final viscosity than the same solutions prepared with cold water and allowed to hydrate slowly. Temperature range of 25–40 °C is desirable for maximum viscosities of guar gum dispersion. The viscosity of 0.5% (w/w) guar solution at 25 °C is significantly higher than that of 37 °C (Srichamroen 2007).
Concentration
Guar gum solution shows very high viscosity even at very low concentration. In most of the food applications it is recommended at below 1% concentration. Guar gum solution viscosities increase proportionally with increases in guar gum concentration (Morris et al. 1981; Robinson et al. 1982). This is due to the interaction of galactose side chain of guar molecule with water molecule. Increase in concentration of guar gum enhances the inter-molecular chain interaction or entanglement which leads to increase in viscosity (Zhang et al. 2005).On doubling the concentration guar gum shows tenfold increase in viscosity (Carlson et al. 1962). Upto 0.5% concentration, guar gum solutions behave as Newtonian system whereas above this concentration level guar solutions behave as non-Newtonian and thixotropic systems. It is also reported that viscosities of different concentration of guar gum at constant temperature reduces with increase in shear rate (Srichamroen 2007).
pH
Guar gum solutions are stable over a wide pH range of about 1.0–10.5. This is due to its non-ionic and uncharged behaviour. Final viscosity of guar gum is not affected by the pH, but the hydration rate shows variation with any change in pH. Fastest hydration is achieved at pH 8–9, however slowest hydration rate occurs at pH above 10 and below 4 (Carlson et al. 1962).
Sugar
In guar-sugar solution, sugar competes with guar gum molecule for the water available in the solution, hence presence of sugar in guar gum solution causes delay in hydration of guar gum molecules. The viscosity of guar-sugar solution decreases gradually and is inversely proportional to the sugar concentration (Carlson and Ziegenfuss 1965). Sweeteners like aspartame, acesulfame-k, cyclamate and neotame do not affect intrinsic viscosity of guar gum solutions significantly (Samavati et al. 2008).
Salt
Salt is most widely used ingredient in foods other than water, its effect on guar gum has been extensively studied (Carlson et al. 1962). Guar gum solutions in brine behave same as in water. Hydration rate is not influenced by salt; however, the presence of sodium chloride slightly increases the final viscosity of fully hydrated guar gum. Physiological buffer i.e. Krebs bicarbonate decreases the viscosity of 0.25% guar gum solution as compared to gaur gum in water alone (Srichamroen 2007). Salts restrict the hydration of guar gum solution (Doyle et al. 2006). Srichamroen demonstrated that viscosity of 0.5% guar gum solution increases with added salts. Presence of salts can help the intermolecular interactions due to change in the charge density and conformation of gum (Gittings et al. 2001).
Food applications
In food industry, guar gum is used as a novel food additive in various food products for food stabilization and as fiber source (Morris 2010). It is liked by both manufacturer and consumer because it is economical as well as natural additive. It is used in variety of foods as an additive because it changes the behaviour of water present as a common component in various foods. Some of the most common food applications of guar gum are shown in Table 3. Permissible use levels and limitations in various products are covered under Title 21 CFR 184.1339, affirming guar’s “generally recognized as safe” (GRAS) status.
Beverages
Guar gum is used in beverages for thickening and viscosity control because of its several inherent properties. The important property of guar gum is its resistance to breakdown under low pH conditions present in beverages. Guar gum is soluble in cold water which makes it easy to use in beverage processing plants. It improves the shelf life of beverages.
Processed cheeses
In cheese product, syneresis or weeping is a problem of serious concern. Guar gum prevents syneresis or weeping by water phase management and thus also improves the texture and body of the product (Klis 1966). In cheese products it is allowed upto 3% of the total weight. Guar gum in the soft cheeses enhances the yield of curd solids and gives a softer curve with separated whey. Low-fat cheese can be produced with addition of guar gum (at concentration 0.0025–0.01% w/v) without changing the rheology and texture compared with full-fat cheese.
Dairy products
Main purpose of using guar gum in frozen products is stabilization. Guar gum has important role in ice cream stabilization because of its water binding properties. Its use in high temperature short time (HTST) processes is very favorable because such processes require hydrocolloids that can fully hydrate in a short processing time. According to McKiernan (1957) locust bean gum has all the properties of an ideal gum but it hydrates slowly which is not favorable in HTST process. Julien (1953) obtained satisfactory results with guar as stabilizer in continuous ice cream processing. Guar gum should be used in ice cream mix at a concentration level of 0.3% (Goldstein & Alter 1959a, b). It was also used in combination with carrageenan in a mixed guar-carrageenan system developed for HTST process. Like locust bean gum its performance can be improved when used in combination with other stabilizers (Weinstein 1958). Guar gum in ice cream improves the body, texture, chewiness and heat shock resistance. Partially hydrolyzed guar gum (at 2–6% concentration level) decreases syneresis and improves the textural and rheological properties of low-fat yoghurt comparable with full-fat yoghurt (Brennan and Tudorica 2008).
Processed meat products
Guar gum has strong water holding capacity in both hot and cold water. Hence, it is very effectively used as a binder and lubricant in the manufacturing of sausage products and stuffed meat products. It performs specific functions in processed meat products like syneresis control, prevention of fat migration during storage, viscosity control of liquid phase during processing and cooling and control of accumulation of the water in the can during storage. Guar gum also enhances the creaming stability and control rheology of emulsion prepared by egg yolk (Ercelebi and Ibanoglu 2010)
Bakery products
Addition of guar gum in cake and biscuit dough improves the machinability of the dough that is easily removed from the mold and can be easily sliced without crumbling. At 1% addition of in batter of doughnuts, it gives desirable binding and film-forming properties that decreases the penetration of fats and oils. Guar gum in combination with starch is found to be effective in prevention of dehydration, shrinking and cracking of frozen-pie fillings (Werbin 1950). In wheat bread dough, addition of guar gum results in significant increase in loaf volume on baking (Cawley 1964). Guar gum along with xanthan gum retard staling in gluten-free rice cakes by decreasing the weight loss and retrogradation enthalpy (Sumnu et al. 2010). Similarly, guar gum also retards staling in chapati at room temperature as well as refrigerated temperature by controlling retrogradation of starch (Shaikh et al. 2008).
Salad dressings and sauces
Its cold water dispersibility and compatibility with high acidic emulsions enable it to use as thickener in salad dressing at about 0.2–0.8% of total weight. In salad dressings, it acts as an emulsion stabilizer by enhancing the viscosity of water phase and hence decreasing the separation rate of the water and oil phase (Goldstein and Alter 1959a, b). Guar gum has been found useful as a thickener in place of tragacanth in pickle and relish sauces (Burrell 1958). Guar gum enhances the consistency of tomato ketchup more prominently than other hydrocolloids like carboxy methyl cellulose, Sodium alginate, gum acacia and pectin. On addition of guar gum serum loss and flow values of tomato ketchup decreases which makes it a novel thickener for tomato ketchup (Gujral et al. 2002).
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Health benefits
Various studies have been conducted on animals to test for both harmful and beneficial effect of guar gum. Guar is completely degraded in the large intestine by Clostridium butyricum (Hartemink et al. 1999). Harmful effects are observed only when the guar gum is given to the animals at a high concentration of about 10–15% on weight basis. This high concentration will reduce growth of animal due to decreased feed intake and impaired digestion. It is considered that the high viscosity of the intestinal tract contents, resulting from intake of guar gum at higher concentration, is the major cause of the negative effects. Hence, guar gum can only be used for its beneficial effects at lower concentration of about 0.5–1.0%. Above this concentration it will show negative effects of higher viscosity, decreased protein efficacy and lipid utilization. High viscosity of guar gum when used at a higher concentration, above 1.0% will not only interfere with nutritional properties of the food but also with the physicochemical and sensory properties of the food product which is not accepted by the consumer. Partial hydrolysis of guar gum (PHGG) reduces the chain length and molecular weight of the polymer and ultimately the lower viscosity makes it a novel soluble fiber that resembles in basic chemical structure with native guar gum and has various applications in clinical nutrition associated with ingestion of dietary fiber. It solves all the problems of high viscosity of guar gum. With hydrolyzed guar gum it is possible to increase the dietary fiber content of various food products like beverages without disturbing the nutritional and sensory properties of the food products. PHGG supplementation to the diet also reduces the laxative requirement, incidence of diarrhea and symptoms of irritable bowel syndrome (Greenberg and Sellman 1998; Slavin and Greenberg 2003). For treatment of irritable bowel syndrome water soluble non-gelling fibers are preferred. Due to its water solubility and non-gelling behavior, partially hydrolyzed guar gum decreased the symptoms in both forms of irritable bowel syndrome i.e. constipation predominant and diarrhea predominant (Giannini et al. 2006).
In vitro study shows that presence of guar gum significantly decreases the digestion of starch. It acts as a barrier between starch and starch hydrolyzing enzymes (Dartois et al. 2010).
Guar gum shows cholesterol and glucose lowering effects because of its gel forming properties. It also helps in weight loss and obesity prevention. Due to gel forming capacity of guar gum soluble fiber, an increased satiation is achieved because of slow gastric emptying. Diet supplemented with guar gum decreased the appetite, hunger and desire for eating (Butt et al. 2007). Mechanism behind cholesterol lowering by guar gum is due to increase in excretion of bile acids in faecus and decrease in enterohepatic bile acid which may enhances the production of bile acids from cholesterol and thus hepatic free cholesterol concentration is reduced (Rideout et al. 2008). Hypotriacylglycerolaemic effects are due to decrease in absorption of dietary lipids and reduced activity of fatty acid synthase in liver (Yamamoto 2001). Toxicity study on partially hydrolyzed guar gum has revealed that it is not mutagenic upto dose level of 2500 mg/day (Takahashi et al.,1994). Adequate intake of guar gum as dietary fiber helps in the maintenance of bowel regularity, significant reductions in total and LDL-cholesterol, control of diabetes, enhancement of mineral absorption and prevention of digestive problems like constipation (Yoon et al. 2008).
