Page 312 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

Syn.: Gelatinum; Grénétine; Houlam

Gelatin is the protein obtained by boiling the collagenous tissues of animals
such as skin, tendons, ligaments, and bones with water, evaporating the aqueous
extract and drying the residue in air.

Preparation
Skin and tendons are first steeped for 15-20 or even 40 days in a dilute milk

of lime. This process dissolves the fleshy matter, removes chondroproteins of the
connective tissues and saponifies fat. The hides, etc., are then thoroughly washed in
running water.

Bones are usually ground and defatted by treatment with benzene or other
organic solvent in closed iron cylinders. After de-fatting, the mineral matter is
sometimes removed by treatment with HCl.

The treated material from the skins, tendons or bones is now heated with water
in open pans with perforated false bottoms or sometimes under pressure. The clear
fluid is run off and is evaporated under reduced pressure until the gelatine content is
about 45 %. It is then run into shallow metal trays or trays with glass bottoms and
allowed to set to a jelly. The jelly is removed and placed in trays with a wire netting
bottom; these trays are passed through a series of drying rooms at temperatures
increasing by about 10ºC each time, from 30ºC to 60ºC; this drying process takes
about a month. Sometimes bleaching by sulphur dioxide is used to produce a light-
coloured product.

Description

Gelatine occurs in colourless or pale yellowish translucent sheets, flakes,
shreds, powder or granules, odour and taste, slight.

Solubility
Gelatine is insoluble in cold water, but swells and softens to an elastic

transparent mass, when immersed in water and gradually absorbs from 5-10 times
its own weight of water. It is soluble in hot water, forming a transparent colorless
liquid which sets to a translucent jelly on cooling, soluble in a cold mixture of
glycerol and water, and in acetic acid. It is insoluble in alcohol 90 %, in benzene, in
ether, in chloroform and in fixed or volatile oils.

Tests for Identity
1- Test for quality: Gelatin should be free from chondrin. An aqueous solution

of Gelatine (1/100) gives a precipitate with chromium trioxide T.S., with tannic
acid T.S., with picric acid T.S. and with solution of lead sub-acetate. The absence

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