Lotus International: Guar Gum Powder

Introduction

Guar gum is derived from the ground endosperm of the guar plant. This ia a hardy and drought- resistant plant which grows 1-2m high with vertical stalks. The seed pods grow in clusters on the vertical stalks. The pods are about 15 cm. long and six to nine seeds about 2-3 mm. in diameter. Roughly, 14-16% of the seeds is the hull, 38-45% represent endosperm, and40-46% germ.
Processing

In commercial processing, a verity of methods are used to separate the guar endosperm from the hull and germ. The hull can be loosened by soaking in water and then removed by charring the hull by flame treatment. Then different grinding is used to separate the germ from the endosperm, since there is a difference in hardness.
pH Value

A 1 % guar sol has a pH between pH 5 and 7. The optimum hydration rate occurs between pH 7.5 and 9. it has a very slight buffering action and is very stable from pH 4 to 10.5. The preferred method to prepare a sol having a very low or very high pH is to prepare a sol at the gum's normal pH and then adjust to as low as pH 1 or slightly above pH 10.5 to give stable sols.
Physical

Guar Gum is practically odorless and has a bland taste. Its color is off-white to very light yellow tan. Mesh sizes are readily available from 40 to 300 BSS.
Solubility

Guar Gum will disperse and swell almost completely in cold or hot water. It is insoluble in organic solvent.
Viscosity

The most important characteristic of Guar is its ability to be dispersed in water and hydrate or swell rapidly and almost completely in cold water to form viscous colloidal dispersions or sols. The viscosity attained is dependent on time, Temperature, concentration, pH, rate of agitation, and particle size of the powdered gum is used. The lower the temperature, the lower the rate at which viscosity increases, and the lower the final viscosity. Above 80c the final viscosity is slightly reduced. The finer guar powder swell more rapidly than coarse powdered gum.
Chemical Characteristics

Guar Gum, like locust bean gum, is a polysaccharide consisting of a straight chain of D--mannopyranose units joined by B *( 1-4) Linkages with a side branching unit of a single D-galactopyranose unit joined to every other mannose unit by a *(1-6) linkages. Locust bean gum has a single galactose side branch every fourth mannose unit. The molecular weight of guar is 220,000 +/-1 0%. The greater side-branching of guar accounts for its cold water hydration as well as its greater hydrogen-bonding activity. An average quality guar gum contains about 80% Galactomannan, 12% Water, 5% Protein, 2% acid insoluble residue or crude fiber, 0.7% Ash, 0.7% Fat, a trace of heavy metals, (arsenic and lead).