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.
[edit]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.[7] However, either borax orcalcium 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 pH extremes at temperature (e.g. pH 3 at 50 °C).[7] 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.[7][8]
[edit]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.
[edit]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.[7]
[edit]Grading
Guar Gum is analysed for
| Test |
Test Method |
Test |
Test Method |
| Colour |
TP/09 |
Acid insoluble residue |
TP/30 |
| Viscosity |
TP/10/04 |
Fat content |
TP/18 |
| Granulation(Mesh) |
TP/21 |
Ash content |
TP/12 |
| Moisture, pH |
TP/1 and TP/29 |
Gum content |
TP/03 |
| Protein |
TP/05 |
Heavy metals |
TP/13 |
| Insolubles Ash |
TP/11 |
Filterability |
TP/20A |
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
