Functional applications of gum arabic arising from physical and structural characteristics
The practical applications depend on the action of gum arabic as a protective colloid or stabiliser, an adhesiveness when in contact with water, its ability to thicken and as dietary food fibre with low calorific value. It can impart its desirable qualities though its influence over the viscosity ,body and texture. It is also a good emulsifier and a foam stabiliser in beverages and when used in spray–dried flavours, since it is capable of film-forming and giving an impenetrable film around the flavour particle. Confectionary applications depend on its ability to interact and bind water, thicken as a gel and so prevent sugar crystallisation. Here also its emulsification quality is important to enable fat to be distributed throughout the product and not move to the surface and make the food appear greasy. In this application as in beverages it needs to be able to coat the fat or oil droplet using its high molecular protein structure.
As a stabiliser in dairy products it needs to prevent water crystallisation and the formation of ice crystals and is thus dependent on its water absorbing properties.
In the baking industry it is used because of its adhesive property, in glazes and toppings.
Similar functionalities are necessary in other application sectors, such as pharmaceuticals where gum arabic is used as a suspending agent, in syrups, emulsions, antiseptic preparations, medicines, wound dressings, cosmetics and adhesives. Having this range of properties is responsible also for is use in paints, inks, lithography and textiles.
Many such applications have suffered because of the variability of the naturally occurring gum arabic. Having a guaranteed specification would allow gum arabic to challenge the synthetic and chemically modified biopolymers which have been coming in to replace it on an application-to-application basis.. The following Table relates a particular application to a specific physical or chemical feature of this versatile polysaccharide.
Gum Applications Overview
| Application | Necessary functionality | Features which need enhancing for best performance |
|---|---|---|
| Emulsification in beverages and confectionary | Coating of an oil or a fat droplet by protein | Ensuring the presence of highest molecular weight protein to enhance binding and emulsification |
| Encapsulation of flavour essential oils; vitamins aromatic compositions, plant essences etc | Forming a hard film to avoid penetration of oxidising agents | Need for increased wetability and good viscosity control – hence a high average molecular weight |
| Bakery for toppings and glazes and to prevent sugar crystallisation and paper to paper adhesion (stamps and cigarette papers) | Adhesion | Need for increased viscoelasticity and shear entanglement of the chains |
| Texture and flavour modification in confectionary | Interact and bind water, to thicken as a gel | Gel formation with enhanced water absorption |
| Chewing gum and confectionary ju-jus, pastilles and gum drops | High water absorption and tenacity | Need high elastic modulus: |
| Foam stabilisation - Structure forming | “lace curtain” effect on beer, marsh mallows and whipping creams | Maximise content of high molecular weight component |
| Fat distribution and fat replacement | salad dressings | Presence of arabinogalactan protein: |
| Dietary Fibre | Dairy products, processed fruits, bakery items, frozen desserts, meat products and food for diabetics | Need ability to fermentation in colon to give short chain fatty acids, with bulking ability |