The application of natural hydrocolloids to foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 179

suspend particles (for example in salad dressings), but fl ows easily when poured.
The exact mechanism of gelation is still under discussion, but is believed to be
due to the long unsubstituted regions along the mannose backbone of LBG. These
regions are able to interact with linear stereoregular hydrocolloid structures such
as xanthan, agar and carrageenan, forming complex gel structures.
LBG is widely used in the food industry for its water-binding and thickening
properties, as a stabiliser, to reduce syneresis and to improve freeze-thaw stability,
and to improve the gel properties of some hydrocolloids. In ambient stable water
jellies it is normally used in combination with carrageenan or xanthan gum to give
the desired texture and stability over the shelf life. It is often found in combination
with xanthan as the gelling system in other desserts and mousses.
LBG is used as a stabiliser in ice cream, in combination with carrageenan and/
or guar gum and/or CMC, to control the growth of sugar and ice crystals, provide
smooth melt down, and heat shock resistance. It is also widely used as a thickener
and stabiliser in hot-prepared sauces, soups, dressings, ketchups and mayonnaise.

8.3.2 Guar gum
Guar gum is the ground endosperm of the guar plant ( Cyamopsis tetragonoloba )
seed, grown mainly in India and Pakistan, but also found in Texas in the US. Guar
is an annual legume that grows mainly in arid and semi-arid regions. In the past,
this has led to large variations in annual availability, mainly due to weather
conditions. This has led to agronomy programmes with guar in other parts of the
world, particularly the southern hemisphere (Wielinga 2009).
The production process for guar gum is simple. The guar seeds are milled to
split them (guar splits) and remove the hull; the guar splits are then hydrated and
milled to a powder. The milled powder fractions are blended to meet the
specifi cations, particularly particle size distribution and viscosity. Purity is also
important as gum products may contain residual hull and germ; hence protein
content and acid insoluble residue (an indication of the residual hull content) are
also specifi ed. The very simple production process makes guar gum an ideal
candidate for natural hydrocolloid status.
Guar gum is a polysaccharide, composed of linear D -mannose units joined by
1,4- β -glycosidic linkages. D -Galactose side chains are linked to the mannose units
by 1,6-linkages. Guar gum has a mannose:galactose ratio of approximately 2:1
(Fig. 8.1). The more highly substituted structure does not leave any long
unsubstituted regions, as seen in LBG, so guar gum cannot interact synergistically
with other hydrocolloids to form gel structures. Some weaker synergy is seen with
xanthan gum, resulting in a viscosity increase, but not gelling. Enzymes can be
used to remove some galactose residues, so that guar gum mimics the behaviour
of LBG in terms of its gelling behaviour with xanthan or carrageenan.
Guar gum is a cold water soluble, non-ionic hydrocolloid. It is an effi cient and
cost-effective thickening agent. Because of its relatively cheap cost in use, it has
been widely used in the food industry as a thickener, often to extend the use of
more expensive hydrocolloids such as xanthan. However, the cost of guar gum is

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