What is gum arabic?

Definition: 
Moroccan Arabic: meska harra المسكة الحرة
Gum arabic is used as a stabilizer, thickener and binder. A natural gum, it's actually the hardened sap of the Acacia senegal or Acacia seyal tree which is common to sub-Sahara Africa as well as Arabia, Egypt and West Asia.
   
Gum arabic, also known as gum acacia, chaar gund, char goond or meska, is a natural gum made of hardened sap taken from two species of the acacia tree; Acacia senegal and Acacia seyal. The gum is harvested commercially from wild trees throughout the Sahel from Senegal and Sudan to Somalia, although it has been historically cultivated in Arabia and West Asia. Gum arabic is a complex mixture of polysaccharides and glycoproteins that is used primarily in the food industry as a stabilizer. It is edible and has E number E414. Gum arabic is a key ingredient in traditional lithography and is used in printing, paint production, glue, cosmetics and various industrial applications, including viscosity control in inks and in textile industries, although less expensive materials compete with it for many of these roles. While gum arabic is now produced throughout the African Sahel, it is also still harvested and used in the Middle East. For example, Palestinians use the natural gum to make a chilled, sweetened, and flavored gelato-like dessert.

                            
                                    Gum Arabic resin ( Gum Acacia, Meska Harra )

Properties and structure of gum arabic:

Technically, gum arabic (acacia senegal) is classed in a group of substances called, oddly, arabinogalactan proteins. More descriptively, it is essentially a very complex polysaccharides, comprised mostly of galactose, arabinose, rhamnose, and glucuronic acid. There is also a very small amount of protein: 18 different amino acids have been identified in acacia senegal, although only four of them comprise more than 10% of the protein, and altogether these amino acids comprise only around 1-2% of the total gum; the other 98-99% is made of the aforementioned sugars.

Gum arabic readily dissolves in water to form highly concentrated solutions of relatively low viscosity, which is a consequence of the gum's highly branched very compact structure. Gum is heterogeneous in nature; at least three discrete components have been identified:

The first, which comprises the greatest part of the gum (~90%), has a molecular weight of about 250,000 and contains almost no amino acids. Analysis suggests that the structure of this component is globular and highly branched.

The second component, comprising around 10% of the total, has a molecular weight of 1,500,000 or so, contains about 10% protein, and is thought by most workers to have what they describe as a "wattle-blossom" structure, consisting of probably five globular lobes of carbohydrate, about 250,000 molecular weight each, which are attached to a common polypeptide chain. The predominant amino acids in this portion are hydroxyproline and serine.

The third component, comprising less than 1% of the total gum, contains 20-50% protein but is not degraded by proteolytic enzymes, suggesting that the protein is located deep in the center of the molecule, available neither to be attacked by enzymes nor to participate in cross linking. The molecular weight of this component is about 200,000 and it is also highly compact. The predominant amino acids in this fraction are aspartic, serine, leucine, and glycine.

Gum Species :

There are more than two dozen species of acacia in the Sudan, but the most important is the Acacia Senegal species. The two species defined for Gum Acacia and the proportion of the market they supply are:
1.    Acacia Senegal - 80%
2.    Acacia Seyal - 20%  

1. Acacia Senegal 

The Acacia Senegal tree is 4-7 m tall with a taproot up to 30 m in depth and a life span of about 25-30 years. The tree can fix nitrogen from the air and grows in poor, sandy, reddish soil, which is caused by the substantial amount of iron present. 65% of the world's supply of Gum Acacia comes from the Sudan.

Throughout the Sudanese province of Kordofan, there are orchards of Acacia Senegal (also called Acacia verek locally), and these are in a belt stretching eastward to the River Nile, and westward through the Province of Darfur. However, in some areas the trees are cultivated and tended in small gardens, and the gum collected from the cultivated tree is colloquially known as ' HASHAB GENIENA' (garden gum). One of the reasons why Kordofan Gum Acacia has an excellent quality is due to the limitation of botanical sources resulting in a uniform product. 90% of the Gum Acacia production in the Sudan is of this high quality.

2. Acacia Seyal
The other species of commercial importance is Acacia Seyal, which grows throughout the African gum belt. Known as Gum Tahla in Sudan and Acacia Grade 2 in Nigeria, Acacia seyal yields a gum, which is not as functional, being weaker in emulsification power due to its different chemical composition.
Several other species of Acacia exude gum, and before today’s segregation of species the gum from these trees was occasionally mixed with other gums. These include A. abyssinica, A. acaciaa, A. laeta, A. orfota, A. stenocaipa.

Gum Arabic benefits:

•    Multifunctional: good emulsifier, film-former, texturizer and low-viscosity water binder and bulking agent.
•    High source of fiber: contains no less than 85% soluble dietary fiber (dry basis)
•    High percentage purity: no additives; free from sediment and impurities; has extremely low bacterial counts
•    Fast hydration and ease of dispersion: available in prehydrated or agglomerated form.
"Natural" labeling: Gum arabic is not chemically modified and qualifies for "natural" labeling or "no artificial additives