Acacia:Indian Gum; Gum Acacia; Gum Arabic

2.2.1.1 Acacia
Synonyms Indian Gum; Gum Acacia; Gum Arabic.
Biological Source According to the USP, acacia is the dried gummy exudation from the stems and branches of Acacia senegal (L.) Willd; family; Leguminoseae, or other African species of Acacia.
It is also found in the stems and branches of Acacia arabica, Willd. Geographial Source The plant is extensively found in India, Arabia, Sudan and Kordofan (North- East Africa), Sri Lanka, Morocco, and Senegal (West Africa). Sudan is the major producer of this gum and caters for about 85% of the world supply.
Cultivation and Collection Acacia is recovered from wild as well as duly cultivated plants in the following manner, such as:
(a) From Wild Plants: The Gum after collection is freed from small bits of bark and other foreign organic matter, dried in the sun directly that helps in the bleaching of the natural gum to a certain extent, and
(b) From Cultivated Plants: Usually, transverse incisions are inflicted on the bark which is subsequently peeled both above and below the incision to a distance 2-3 feet in length and 2-3 inches in breadth. Upon oxidation, the gum gets solidified in the form small translucent beads, sometimes referred to as  ‘tears’. Tears of gum normally become apparent in 2-3 weeks, which is subsequently hand picked , bleached in the sun, garbled, graded and packed.
Description
Colour: Tears are usually white, pale-yellow and sometimes creamish-brown to red in colour. The power has an off-white, pale-yellow or light-brown in appearance.
Odour: Odourless (There is a close relationship between colour and flavour due to the
presence of tannins).
Taste: Bland and mucillagenous.
Shape & Size: Tears are mostly spheroidal or ovoid in shape and having a diameter of about 2.5-3.0 cm.
Appearance: Tears are invariably opaque either due to the presence of cracks or fissures pro-duced on the outer surface during the process or ripening. The fracture is usually very brittle in nature and the exposed surface appears to be glossy.
Chemical Constituents Acacia was originally thought to be composed only of  four chemical constituents, namely : (–) arabinose; (+) – galactose; (–)–rhamnose and (+) glucuronic acid.

On subjecting the gum acacia to hydrolysis with 0.01 N H2SO4 helps in removing the combined product of (–) – arabinose and (+) – galactose, whereas the residue consists of the product (+) – galactose and (+) – glucuronic acid. These two products are formed in the ratio of 3:1.

It also contains a peroxidase enzyme.

Chemical Tests
1. Lead Acetate Test: An aqueous solution of acacia when treated with lead-acetate solution it yields a heavy white precipitate.
2. Borax Test: An aqueous solution of acacia affords a stiff translucent mass on treatment with borax.
3. Blue Colouration due to Enzyme: When the aqueous solution of acacia is treated with benzidine in alcohol together with a few drops of hydrogen peroxide (H2O2), it gives rise to a distinct–blue colour indicating the presence of enzyme.
4. Reducing Sugars Test: Hydrolysis of an aqueous solution of acacia with dilute HCl yields reducing sugars whose presence are ascertained by boiling with Fehling’s solution to give a brick-red precipitate of cuprous oxide.
5. Specific Test: A 10% aqueous solution of acacia fails to produce any precipitate with dilute solution of lead acetate (a clear distinction from Agar and Tragacanth); it does not give any colour change with Iodine solution (a marked distinction from starch and dextrin); and it never produces a bluish-black colour with FeCl3 solution (an apparent distinction from tannins).
Uses
1. The mucilage of acacia is employed as a demulscent.
2. It is used extensively as a vital pharmaceutical aid for emulsification and to serve as a thickening agent.
3. It finds its enormous application as a binding agent for tablets e.g., cough lozenges.
4. It is used in the process of ‘granulation’ for the manufacture of tablets. It is considered to be the gum of choice by virtue of the fact that it is quite compatible with other plant hydrocolloids as well as starches, carbohydrates and proteins.
5. It is used in conjuction with gelatin to form conservates for microencapsulation of drugs.
6. It is employed as colloidal stabilizer.
7. It is used extensively in making of candy and other food products.
8. It is skillfully used in the manufacture of spray – dried ‘fixed’ flavours – stable, powdered flavours employed in packaged dry-mix products (puddings, desserts, cake mixes) where flavour stability and long shelf-life are important.

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