2.2.1.3 Karaya Gum
Synonyms Gum Karaya; Kadaya; Katilo; Kullo; Kuteera; Sterculia; Indian Tragacanth; Mucara.
Biological Source Karaya Gum is the dried exudate of the tree Sterculia urens Roxb; Sterculia villosa Roxb; Sterculia tragacantha Lindley and other species of Sterculia, belonging to the family: Sterculeaceae. It is obtained from Cochlospermum Geographical Source: gossypium, De Candolle or other species of cochlospermum Kunth –family: Bixaceae.
Geographical Source The S. urens is found in India especially in the Gujarat region and in the central provinces.
Preparation The gum is obtained from the Sterculia species by making incisions and, thereafter, collecting the plant excudates usually after a gap of 24 hours. The large irregular mass of gums (tears) which weigh between 250 g to 1 kg approximately are hand picked and despatched to the various collecting centres. The gum is usually tapped during the dry season spreading over from March to June. Each healthy fully grown tree yields from 1 to 5 kg of gum per year; and such operations may be performed about five times during its lifetime. In short, the large bulky lumps (tears) are broken to small pieces to cause effective drying. The foreign particles e.g., pieces of bark, sand particles, leaves are removed. Thus, purified gum is available in two varieties, namely:
(a) Granular or Crystal Gum: Having a particle size ranging between 6 to 30 mesh, and
(b) Powdered Gum: Having particle size of 150 mesh
Description
Colour : White, pink or brown in colour
Odour : Slight odour resembling acetic acid
Taste : Bland and mucilageous taste
Shape : Irregular tears or vermiform pieces.
It is water insoluble but yields a translucent colloidal solution.
Chemical Constituents Karaya gum is partially acetylated polysaccharide containing about 8% acetyl groups and about 37% uronic acid residues. It undergoes hydrolysis in an acidic medium to produce (+)–galactose, (–)–rhamnose, (+)–galacturonic acid and a trisaccharide acidic substance. It contains a branched heteropolysaccharide moiety having a major chain of 1, 4-linked α–(+)–galacturonic acid along with 1, 2-linked (–)–rhamnopyranose units with a short (+)–glucopyranosyluronic acid containing the side chains attached 1→3 to the main chain i.e., (+)–galactouronic acid moieties.
Chemical Test It readily produces a pink colour with a solution of Ruthenium Red.
Substituent/Adulterant It is used as a substitute for gum tragacanth.
Uses
1. It is employed as a denture adhesive.
2. It is used as a ‘binder’ in the paper industry.
3. It is also employed as a thickening agent for dyes in the textile industry.
4. It is widely used as a stabilizer, thickner, texturizer and emulsifier in food
5. It is used as a bulk laxalive.
6. It finds its usage in lozenges.
7. It is employed extensively in wave set solution and in skin lotions.
8. It is used in preparations concerned with composite building materials.
