Thursday, May 17, 2012

GUAR GUM- PROPERTIES AND STRUCTURE


BY PRODUCT OF GUAR- GUAR GUM
The seeds of the guar plant have three parts i.e. the germ, the endosperm and the husk. The popular guar gum, which used in mining, petroleum drilling and textile manufacturing sectors, is obtained from the endosperm of the seed of the plant. The gum is refined to make a yellowish white powder and it is consumed worldwide in this powder form only.
From Guar plant‘s (Cyamopsis tetragonolobus) endosperm Guar Gum is derivative. Guar is a legume (a plant of pea family) crop grows best in sandy soils and needs moderate, flashing rainfall with lots of sunshine. Guar gum is found in the seeds of two annual leguminous plants (Cyamopsis tetragonolobus and psoralioides).
Guar gum is useful as a thickening agent for water and as a reagent for adsorption and hydrogen bonding with mineral and cellulosic surfaces. It is an edible carbohydrate polymer.
It is non-ionic, free flowing, low pale white colored, coarse to fine grounded powder and is water-soluble hydrocolloids.
Guar gum is used as a thickener and emulsifier in commercial food processing. It has almost 8 times the thickening power as corn starch, and is used in dressings, sauces, milk products, and baking mixes. It is also used in paper manufacturing, textiles, printing, cosmetics and pharmaceuticals.

Properties:
Guar gum is an emulsifier, thickener, and stabilizer approved for use in a wide range of foods, cosmetics, and pharmaceuticals. It is sold as a white to yellowish odorless powder, which is available in different viscosities and different granulometries depending on the desired viscosity. Its viscosity is a function of temperature, time, and concentration. One advantageous property of guar gum is that it thickens without the application of heat. Guar Gum has the following properties, which make it useful in variety of applications.        
The guar gum is a polysaccharide which in water gives hexose sugar, mannose and galactose. These hexose sugars are soluble both in cold and hot water but it is insoluble in most of the organic solvents. In water it gives high viscosity even used small quantity. Strong acids cause hydrolysis and loss of viscosity; alkalies in strong concentration also tend to reduce the viscosity. Adding borax solution will form a gelatinous mass. Guar gum is compatible with starch, alginate, agar etc.
It is easily soluble in both hot and cold water.
Properties of film forming.
Remains stable in solution over wide range of pH values from

5-7.
Good thickening agent.
High viscosity.
Resistance to oils, greases and solvent.
Capacity of Water binding.
Functioning at low temperatures.
Compatible with many other hydrocolloids used in food

formulations.
Versatility due to number of free hydroxy groups to

make derivatives for specific applications.

Standard:
Minimum standards for good quality Guar Gum Powder have been defined in the United States FCC and by European Union Specification, E-412 as under.
Moisture :
Max. 12.00%
pH :
Max. 6.00 To 7.00
Protein : 
Max. 04.60%
Ash(total) : 
Max. 02.50%
Galactomannan : 
Min. 80.00%
Viscosity, 1%, as is, cps,
2 hrs 3,500-5,500
24 hrs min. 90% of the 2-hr value
1% solution, 25°C, Brookfield RVT, Spindle 3 or 4.20 rpm.
Particle size, %
Through U.S. 60,min. 98
Through U.S. 200 max. 10
Typical Microbial Content
Aerobic Plate Count  :  10,000 / gm.
Yeast & Mould            :        500/ gm.
Coliform                       :         50/ gm.
E.Coli & Salmonella   :           absent

Guar Extracts:
Guar Split/Gum 28% (+/- 1% variance) extracts from Guar seed.
The ratio of Churi and Korma 67% depending upon the quality of the seed.
Split/Gum is further refined to Guar Powder
Churi and Korma are used for Cattle Feed
Guar Gum Chemical Stucture          
Guar Gum mainly consists of hydrocolloidal polysaccharide with a high molecular weight, which consists of galactopyranose- and mannopyranose- units in glycoside linkage which can be chemically described as galactomannan. The main chain consists of (1-4) linked beta-D mannose residues and the side chain of (1-6) linked alpha-D galactose. 
Guar gum has an overall ratio of mannose to galactose of around 2 : 1. Guar Gum has excellent cold water solubility because of the high galactose: mannose ratio.
The molecular weight of Guar has reported as 1-2 x 10 6. Further studies indicate that Guar Gum is a rigid rod like polymer because of the beta linkage between the monomer units. Guar hydroxylsare in the CIS position. The CIS position is important since adjacent hydroxyl groups reinforce each other in hydrogen bonding reactions.
Guar Gum : Structure Diagram   
Guar Gum Chemical structure
Guar Gum Chemical Properties 
  • Guar gum is an economical thickener and stabilizer. It hydrates fairly rapidly in cold water to give highly viscous pseudo plastic solutions of generally greater low-shear viscosity when compared with other hydrocolloids.
  • High concentrations (~ 1%) are very thixotropic but lower concentrations (~ 0.3%) are far less so.
  • Guar gum is also emulsifier as it has more galactose branch points.
  • It does not form gels but does show good stability to freeze-thaw cycles.
  • Guar gum shows high low-shear viscosity but is strongly shear-thinning. Being non-ionic, it is not affected by ionic strength or pH but will degrade at pH extremes at temperature for e.g. pH 3 at 50°C. With case in, it becomes slightly thixotropic forming a biphasic system containing casein micelles.
  • Guar gum retards ice crystal growth non-specifically by slowing mass transfer across solid/liquid interface.
  • Guar Gum is known as one of the best thickening additives,emulsifying additives and stabilizing additives.
  • Guar gum has a polymeric structure, containing several hydroxyl groups. The various derivatives or industrial grades of Guar gum are manufactured by reaction of these hydroxyl groups with chemicals that aid in:
    • Dispersion
    • Control Viscosity
    • Causing Gelling
    • Act as preservatives
Quality:               
Guar gums quality assurance  examines the quality of raw materials, semi-finished and finished products. Following physical & chemical analysis of Guar Gum.
  Odour
  Acid insoluble residue
  Colour
  Ash content
  Viscosity
  Gum content
  Granulation
  Heavy metals
  Moisture, pH
  Insoluble
  Protein
  Filterability
  Fat content

The microbiological performs bacteriological process control & testing of food grade products. Formulates microbiological analyses and testing.
  Standard plate count
  E-coli
  Yeast count
  Salmonella
  Mold count
  Staphylococcus
  Coli form
  Pseudomonas

2 comments:

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