Guar Gum

Guar Gum

Agronomy & Manufacture

Guar Gum is derived from the seeds of the Guar plant “Cyamopsis tetragonalobus”. It is an annual plant, about 4 feet high, vertically stalked, with large leaves and clusters of bean-like pods.  Each pod is about 5-8 CMS long and has on an average 6-9 small, grayish-white pea shaped seeds. Guar is a hardy, drought resistant bush, which grows well in the semi arid areas of west and north-west India and parts of Pakistan.  Guar grows best in sandy soils, If needs moderate, intermittent rainfall with lots of sunshine.  Too much precipitation can cause the plant to become more “ leafy” thereby reducing the number of pods and/or the number of seeds per pod, which affects the size, and yield of seeds. The crop is sown after the first rains in July and harvested in late October.  The Pods are then sun dried, manually separated from the seeds and the seeds are supplied to the industry for processing. Tender green Guar  pods are also consumed as a vegetable and cattle-feed in India.

The Guar seeds are dicotyledonous having a diameter of about 2.0-3.0 mm. The seeds make-up about 60 % -70 %  of the pod weight.  The germ is completely enveloped by the 2 halves of the endosperm, and if is the endosperm that is the source of the gum. The tough seed skin or husk is of a fibrous nature, composed of compressed thin layers of cellulosic material.

The gum is commercially extracted from the seeds essentially by a mechanical process of roasting, differential attrition, sieving and polishing.The seeds are broken and the germ is separated from the endosperm .  2 halves of the endosperm are obtained from   each seed and are known as Undehusked Guar  Splits.  When the fine layer of fibrous material, which forms the husk, is removed and separated from the endosperm hales by polishing, Refined Guar Splits are obtained. The husk and germ are rich in protein and form a valuable cattle-feed.  The larger germ particles have a high content of oil and albuminoids (o&a) – about 55% The smaller germ particles have an o & a content of about 40% and the husk about 25% o & a. Various standardized blends of these “Guar meals” can be made to achieve standard o &a contents.  Guar meal may also be toasted to reduce odour and remove trypsin inhibitors.  This is known as toasted Guar meal and is sold in the international markets.  This product is usually standardized of 45%  o&a content.

The refined Guar splits are then treated and finished into powders by a variety of routes and processing techniques depending upon the end product desired.  High purity  Guar gums like Guar gum for foods.  Feeds and pharmaceutical applications can be produced in many different viscosities hydration to suit specific applications.  Various modified/derivatised Guar gums such as hydrolyzed, hydroxyalkyl, carboxyalkyl, oxidised, sulphated, borated, cationic and various combination of these are commercially useful for a number of industry applications.

Chemistry & Structure

Guar gum Guar Gum is a plant seeds hydrocolloid a cold and hot water soluble galactomannan polysaccharide.  Chemically, Guar gum is composed of  beta 1,4 linked linear mannose backbone chain with single galactose side  unit on approximately every other mannose unit, in a 1,6 alpha linkage.

The molecular structure reveals that it is a rigid rod-like polymer due to the beta linkage between the monomer units. The mannose to galactose ratio has been estimated at 1,8:1 to 2:1.

Recent studies indicate that the galactose side units may not follow a regular spacing pattern, but in fact, may appear in “cluster” and on either side of the mannose backbone.

Guar Gums

Guar gum brings about stabilization, often in combination with  other hydrocolloids, by modifying and controlling the behavior of water in a food or feed. Guar gum may act as the primary  or supporting stabilizer ingredient.

in various frozen dairy and non-dairy products like ice-creams, ice-milk, ice candies, sherbets, milk shakes etc. , guar gum,  either alone  or in combination with other hydrocolloids like carragenan and locust bean gum is used to prevent the formation of ice crystals during freeze- thaw cycles, to impart a smooth and creamier texture to the product, to increase overrun and improve chewiness. Guar gum prevents quick meltdown and increases shelf-life.

in cottage cheese dressings. Guar gum promotes curd integrity by lubricity and binds the free water to yield a homogeneous stable product. In soft cheese products processed cheese spreads and dips the use of guar gum helps eliminate syneresis and improve texture and flavour due to better control of moisture and fat/oil migration. Guar gum also increases yield, aids drainage and imports a soft, compact and tender texture to recovered curd.

in various baked goods, the use of  guar gum promotes a dough having excellent firm properties particularly in low gluten flour baked goods like rolls and breads with guar gum have on improved shelf life due to better moisture retention, softer textures and higher loaf volume on baking. Cake and biscuit doughs benefit by incorporating  guar gum leading to better softness, better mould release and less crumbling during slicing  in dry cake-mixes, guar gum offers several advantages – if aids one step mixing , gives shorter batter mix time, yields improved internal structure, prolongs shelf-life, improves application of icings and frostings and permits freezing of the cake.

the use of guar gum in juices nectars  and syrups helps in the homogenous dispersion of pulp during filling and storage guar gum also leads to improved mouthfeel in these products. In fruit based beverages, guar gum helps in solids suspension and can be effectively combined with emulsifiers to prevent separation of flavour oils in the container.

in canned foods and canned pet-foods, guar gum is widely used as a viscosifier, processing aid and protective colloid. Guar gum offers the advantages of less wastage  due to splattering during the working process, easier pumping of  finished product to filling equipment less splashing and therefore more accurate control during can filling and a homogenous dispersion of solids in the liquid phase throughout the filling process. The finished  goods augmented with guar gum exhibit good storage stability as there is no migration of fat, and the water and solids are maintained in a goods emulsion state. In conned pet-foods removal of the product form the can is also easier due to the friction reducing properties that guar gum imports. A partial replacement of starch and flour with guar gum in conned foods helps to reduce sterilization and cooling time since if acts as a protective colloid to reduce starch retrogradation.

Guar gum is used as an effective viscosifier in soups, sauces and gravies, either alone or in combination with xanthan gum and is complimentary to the use of starches. Guar gum helps provide a uniform viscosity to the product over a wide temperature range and imparts goods cling to sauces and graves.

in pourable salad dressings, guar gum is often used with xanthan gum and propylene glycol alginate. Guar gum helps to enhance the mouthfeel, gives controlled pourability, suspension of solids and improved cling.

Guar Gums Powder

Due to guar gum’s excellent cold and hot water solubility, if can be very effectively used in instant  products like soup and sauce mixes, instant drinks and desserts.

Guar gum is also used in various restructured or fabricated foods for better water retention and paste workability and integrity before the final structuring of the fabricated food. Guar gum is also used as an additive in food extrusion applications due to its excellent water holding and friction reducing capabilities.

Guar gum’s capabilities to retain moisture and prevent sugar recrystallisation are taken advantage of in icings, glazes, frozen whipped toppings and breading.

Guar gum is also used in the preparation of noodles and pasta products in pickles and relishes and in canned sea foods,

Fish feed formulations  incorporate guar gum in the dry - mix which aids in the making of on excellent homogeneous fish feed paste when reconstituted with water and fresh minced fish. Guar gum is also used as a binder in feed pellets.


Guar gum, besides its major function of water retention viscosifying and thickening is also finding increased use in foods as :


  • A source of natural water-soluble fiber.
  • To improve mouthfeel and texture in low fat/no fat foods, especially in combination with certain starches and other hydrocolloids like micro-crystalline cellulose.
  • In slimming aids and dietetic foods.
  • In products requiring “all natural” labeling.
  • As a binder, firm former and protective colloid.
  • As a stabilizer in sour dairy products.



In pharmaceuticals, guar gum finds use in :

  • Tablets, as a binding and disintegrating agent.
  • As a controlled release agent in drug formulations.
  • As a slimming and appetite control agent.
  • Diabetic formulations for controlling blood sugar level.
  • Cholesterol reducing formulations.
  • Antacids.
  • Suspensions and syrups.
  • Laxative formulations.
  • Tooth pastes.

Depolymerised Guar Gum

The molecular weight of guar gum has been estimated at 180,000 to 220,000.

Depolymerised guar gum products have significantly lower molecular weights. usually, viscosities can be directly related to the molecular weight.  

In general, if is the high galactose (to mannose) molar ratio that accounts for the excellent cold water solubility  of guar gum. As important feature of guar gum guar gum structure to be noted is the cis-position of the adjacent hydroxyl groups on the c2 and c3 in  the mannose and c3 and c4 in the case of galactose. This is an important factor since these adjacent hydroxyl groups reinforce each other in hydrogen bonding reactions.

the 3 “free” hydroxyl groups per anhydro galactose/mannose building block (sugar unit) are available for substitution and etherification.   the guar polymer chain length can also be reduced by various depolymerisation processes like hydrolysis, oxidation, enzymatic and thermal degradation techniques. These technologies are used to import specific properties to the product to suit various applications.

Properties:

guar gum is a non –ionic, white to cream –white powder, soluble in hot and cold water, but insoluble in most organic solvents. It is commercially used in foods, feeds and pharmaceuticals for its excellent ability to control rheology by economic water phase management, If is neutral in taste, but may have a slight characteristic “grassy or beany"  odour.

guar gum forms highly viscous colloidal dispersions when hydrated in cold water.   these solutions exhibit non-newtonian, pseudo-plastic rheological properties. Aqueous solution viscosities decrease with increasing rates or shear.

guar gum aqueous dispersions, like most hydrocolloids, obey the power law.

the lower the value of n, the greater the shear thinning effect (loss of viscosity on  increasing shear). For an ideal newtonian fluid, the viscosity is independent of shear and therefore n =1. Numerous studies have shown that solutions with a high “n” value  tend to feel slimy in the mouth. Therefore, when high viscosities and a good, clean mouthfeel are desirable, hydrocolloids like guar gum with low “n “ values are the gums of choice. The value of the  power law constants  vary with different concentrations of guar gum.

Guar gum solution viscosities increase exponentially with increasing concentration of guar gum in water in addition to shear rates and polymer concentration, guar gum solution viscosities are also influenced by previous shear history, temperature, ph and the presence of salts and other solids.   the time required for  guar gum to completely hydrate in water and reach peak  viscosities depends upon the grade of guar gum, the dispersion and stirring equipment used the ph and temperature.
Guar gum viscosities will tend to reduce if the dispersions is sheared of very high speeds at very high speeds for extended periods. such a reduction is more pronounced at elevated temperatures and extremes of ph. Guar gum is stable over a wide ph range due to the non-ionic nature of the product, almost constant viscosity is maintained in the ph range of 3-10. The optimum ph range for hydration of guar gum is 5. 5-6. 5.

Guar gum’s properties to rapidly hydrate in cold water and yield high viscosities; its pseudoplastic theology and its relative stability over a wide ph and temperature range make it a highly efficient in many food stability systems. Any food requiring the scientific management of its water  phase is a potential application for guar gum. Guar gum is used as a stabilizer, thickener, viscosifier rheology control agent, bodying and suspension agent, texture and consistency modifier etc.

Guar Gum Uses

Guar gum, besides its major function of water retention viscosifying and thickening is also finding increased use in foods as :

  • A source of natural water-soluble fiber.
  • To improve mouthfeel and texture in low fat/no fat foods, especially in combination with certain starches and other hydrocolloids like micro-crystalline cellulose.
  • In slimming aids and dietetic foods.
  • In products requiring “all natural” labeling.
  • As a binder, firm former and protective colloid.
  • As a stabilizer in sour dairy products.

 

 In pharmaceuticals, Guar gum finds use in :

 

  •  Tablets, as a binding and disintegrating agent.
  •  As a controlled release agent in drug formulations.
  •  As a slimming and appetite control agent.
  •  Diabetic formulations for controlling blood sugar level.
  •  Cholesterol reducing formulations.
  •  Antacids.
  •  Suspensions and syrups.
  •  Laxative formulations.
  •  Tooth pastes.

 

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