Hydrocolloids:
Stabilisers, Thickeners and Gelling Agents > GUAR GUM
GUAR GUM
Application
Guar gum is used as a thickener in sauces, salad dressings,
as an agent in ice cream that prevents ice crystals from
forming, and as a fat substitute that adds the "mouth
feel" of fat.
In pastry fillings, it prevents "weeping" (syneresis)
of the water in the filling, keeping the pastry crust crisp.
It has a very high viscosity (thickness) even when very
little is used.
When mixed with xanthan gum or locust bean gum, the viscosity
is more than when either one is used alone, so less of each
can be used.
| APPLICATION |
FUNCTION |
| Soups, sauces and marinades |
Viscosity control. |
| Pastry fillings |
Viscosity and syneresis control. |
| Ice Cream |
Ice crystal and Viscosity control. Fat mimetic. |
Chemistry
Guar gum (E412) is a polysaccharide
(a long chain made of sugars) composed of galactose and
mannose.
Guar gum comes from the endosperm of the seed of the legume
Cyamopsis tetragonolobus, which
is an annual plant grown in arid regions of India.
Properties
Guar gum is an economical thickener
and stabiliser. It hydrates fairly rapidly in cold water
to give highly
viscous, pseudoplastic 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 concentration or pH but will
degrade at pH extremes at temperature (e.g. pH 3 at 50°C).
It shows viscosity synergy with xanthan gum. With casein,
it becomes slightly thixotropic forming a biphasic system
containing casein micelles.
When guar gum is dissolved in hot or cold water, it takes
around 4 hours to reach maximum viscosity.

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