This gum consists of endosperms of the seeds of Ceratonia siliqua Linn., belonging to family Leguminosae.
LOCUST BEAN GUM
Synonyms
Arobon, Carob gum, Ceratonia.
Biological Source
This gum consists of endosperms of the seeds of Ceratonia siliqua Linn., belonging to family Leguminosae.
Geographical Source
The plant is found in Cyprus, Sicily and Egypt. It is
cul-tivated easily but very sensitive to low temperature. It is produced in
Spain, Greece, Algeria, Morocco, Israel, Italy and Portugal.
History
The cultivation of locust bean trees was known before
Christian era. Dioscorides referred its curative properties in the first
century A.D. In
Sicily, the carob trees were probably planted in 16th century. Arabs used carob
seed as a unit of weight and it was labelled as carat, which in turn has become
unit of weight for precious stones.
Cultivation and Collection
Carob is an evergreen tree growing to a height of about 10 m
and has luxuriant perennial foliage. The tree grows on rocky soil and has very
long roots that penetrate up to 18–25 m and survive in an area where there is
very little rain fall.
It starts bearing fruits only after three years. The plants
start flowering in January to March every year, and the fully matured fruits
are ready by October–November. The fruits (pods) are harvested by shaking the
twigs and picked up from the earth by hand and sent to market.
The locust bean fruits or carob are dark chocolate coloured,
10–20 cm long, 2.0–5 cm wide and 0.5–1.0 cm thick. The seeds are ovoid dark
brown, very hard and weigh 0.21 g or 3.2 grains (i.e. one Carat). The locust
bean tree can be planted or even grafted.
Preparation and Purification of Gum
Locust bean pods consist of 90% of pulp and 8% of kernels.
The pods are fed to kibbling machine. The kernels separated consist of 30–33%
of husk, germ (about 25%) and endosperm (42–46%). Preparation of high quality
gum consists of separation of endosperm from embryo. Successful removal of
outer dark coloured husk decides the quality of the gum. Decorticated seeds
(dehusked seeds) split lengthwise and are separated from the embryo. The
presence of yellow germ (i.e. embryo) increases the rate of fermentation of the
gum solutions in further products. Hence, it must be thoroughly removed from
the endosperm. It is then pulverized and graded according to the mesh size. The
normal mesh sizes available in Italian market are 150, 175 and 200.
Description
Chemical Constituents
Locust bean gum contains about 88% of
D-galacto-D-man-noglycan, 4% pentan, 6% protein, 1% cellulose, and 1.0% ash.
The ratio of D-galactose to D-mannose is approximately 20:80. Commercial locust
bean gum contains no specks and gum particles should not exceed 8–10%. The
natural moisture content of gum is about 14.0%.
Identification Test
Locust bean gum mucilage when boiled with 5.0% potassium
hydroxide solution becomes clear and shows no yellow colour as in agar and
tragacanth or brown colour as in sterculia gum.
Uses
It is useful as a stabilizer, thickner and binder in
cosmetics; adsorbent and demulcent therapeutically. It is used as sizing and
finishing agent in textiles and also as drilling mud addi-tive. In food
industry, it is used as substitute for starch.
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