The application of natural hydrocolloids to foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 185

The gum is a polysaccharide containing a mixture of D -galactose, D -glucuronic
acid, L -rhamnose and L -arabinose. What is very unusual about gum arabic
compared with other hydrocolloids is that it contains a proteinaceous core. The
protein fraction makes up less then 2% of the acacia gum, but is crucial to the
gum's functionality - treatment with proteolytic enzymes to remove the protein
component results in a loss of emulsifi cation ability.
Gum arabic is very soluble in water (even cold water). It has a lower
viscosity than other hydrocolloids, only becoming viscous at high concentrations,
enabling concentrations as high as 30-50% to be prepared. The other major
functional property of gum arabic is its ability to act as an emulsifi er for oils and
fl avours. The protein-rich components preferentially absorb onto the surface of oil
droplets, stabilising them, while the carbohydrate blocks prevent fl occulation and
coalescence.
The two main application areas for gum arabic are in the confectionery and
beverage industries. Gum arabic is used as the main texturing agent in solid gum
drops and pastilles, or with gelatin for a softer, wine gum type texture (Benech
2005). In aerated confectionery, gum arabic acts as a foam stabiliser, while in
toffees it is used to emulsify the fat in the formulation. Another major use of gum
arabic in the confectionery industry is as a fi lm forming and coating agent, for
example, on nuts or chocolates. If a sugar coating alone is used to form the hard
shell, fat migration from the nut or chocolate centre can occur. Therefore, the
product is coated in a fi lm of gum arabic before adding the sugar coating. Gum
arabic is also a key component of the hard coatings of chewing gum.
Gum arabic is stable in acid conditions and is widely used as the emulsifi er in
the production of concentrated citrus or cola fl avour emulsions for application in
soft drinks. The gum maintains a stable emulsion during the storage of both
the beverage oil emulsion and the fi nished beverage. A third use is for the
production of encapsulated fl avours, transforming volatile liquid fl avours into
a fl owable powder. This extends the application areas into powdered products
and also gives the fl avour oil much better stability to oxidation. Encapsulation
involves spray drying an emulsion of the fl avour oil, where gum arabic has been
used as the emulsifi er. Gum arabic can also be used to encapsulate other
ingredients, including natural colours, polyunsaturated fatty acids, vitamins and
neutraceuticals.
There is also interest in gum arabic as a source of soluble fi bre and the main
manufacturers of gum arabic market specifi c types for this purpose. Unlike other
hydrocolloids, it can be added to products at relatively high concentrations without
signifi cantly increasing the viscosity and texture, thus enabling it to contribute
signifi cantly to a fi bre claim on a food product. It is also claimed to have prebiotic
properties.
Gum arabic is a natural hydrocolloid with a simple manufacturing process and
some unique functionality. Its historical use goes back more than 3000 years,
being used by the Egyptians for embalming mummies and in paints for their
hieroglyphic paintings. However, over the last 30 years there have been
considerable fl uctuations in supply, owing to drought and political unrest in the

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