Leung's Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics

3. B. L. Oser et al.,Food Cosmet. Toxicol., 3 ,
   563 (1965).
   4. Monograph Guajaci lignum Bunde-
   sanzeiger, no. 76 (April 23, 1987).

GUAR GUM

Source:Cyamopsis tetragonoloba(L.) Taub.
(syn.C. psoralioidesDC.) (Family Legu-
minosae or Fabaceae).

Common/vernacular names: Guar flour, jag-
uar gum.

GENERAL DESCRIPTION

Guar gum is derived from the seed of the guar
plant. The guar plant is a small nitrogen-fixing
annual that bears fruits known as legumes
(pods) containing five to nine seeds per pod;
up to about 1.8 m high. It is believed to be
native to tropical Asia and has been grown in
India and Pakistan for centuries as food for
both humans and animals. It was introduced
into the United States in the early 1900s and is
now grown in Texas and Oklahoma. Major
guar producers are India, Pakistan, and the
United States.
Part used is the endosperm of the seed. The
endosperm constitutes 35–42% of the seed; it
is separated from the outer components of the
seed (seed coat or hull and embryo or germ)
during processing. Processing involves hull
removal by water or acid soaking and grind-
ing, followed by preferential grinding to re-
move the embryo. The endosperm left is then
ground to a fine powder, which is commercial
guar gum.
There are different grades of guar gum with
varying amounts of the hull and germ present
as the main impurities. Food- and pharmaceu-
tical-grade guar gum is a white to yellowish
white, nearly odorless powder. It is easily
dispersed in cold or hot water (seelocust bean
gum) to form solutions (sols) with a slightly
acidic to almost neutral pH (5.4–6.4). The rate
of hydration (dispersion) is dependent on its

particle size, water temperature, and the rate

of agitation. Its optimal rate of hydration

occurs between pH 7.5 and 9. Even at low

concentrations (1–2%), guar sols have high

viscosity and form gels with borate ions at

alkaline pH values as locust bean gum and

aloe vera gel; these gels can be liquefied

by lowering the pH below 7, by heating,

or by adding simple polyols (glycerol,

mannitol, etc.) that can react with the borate

ions. The borate gels are not edible. Guar gum

is not soluble or dispersible in organic

solvents.

Theviscosity of guargum sols is unaffected

by pH changes between 4 and 10.5.

Guar gum is reported to be compatible with

gelatin, starch, and most water-soluble gums

(e.g. acacia, agar, algin, karaya gum, locust

bean gum, pectin, and tragacanth).

CHEMICAL COMPOSITION

Commercial food-grade guar gum is reported

to contain usually about 80% guaran (a ga-

lactomannan), 5–6% crude protein, 8–15%

moisture, 2.5% crude fiber, 0.5–0.8% ash, and

small amounts of lipids composed mainly of

free and esterified fatty acids.^1

Guaran (the pure galactomannan from guar

gum) is a polysaccharide with a primary

structure consisting of regular repeating

units of the trisaccharide 4-O-(6-O-a-D-galac-

topyranosyl-b-D-mannopyranosyl)-b-D-manno-

pyranose. Its molecular weight has been re-

ported to be around 220,000 (WHISTLER AND

BEMILLER).^2

PHARMACOLOGY AND BIOLOGICAL

ACTIVITIES

Guar gum has been reported to lower the

serum and liver cholesterol levels in chickens

Guar gum 347