Guar Gum : Overview
The molecular structure reveals that GUAR GUM is a straight chain galactomannan with galactose on every other mannose unit. Beta 1-4 Glycosidic linkages couple the mannose units and the galactose side chains are linked through alpha 1-6. The mannose to galactose ratio has been estimated at 1.8 : 1 to 2: 1.
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 has excellent cold water solubility because of the high galactose: mannose ratio. The special properties of GUAR GUM
known in india make it most suitable for various industrial applications.
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 and much greater than that of locust bean gum.
- High concentrations (~ 1%) are very thixotropic but lower concentrations (~ 0.3%) are far less so.
- Guar gum is more soluble than locust bean gum and a better emulsifier as it has more galactose branch points.
- Unlike locust bean gum, 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:
- Control Viscosity
- Causing Gelling
- Act as preservatives