Food Structure


Hydrocolloids are water-soluble biopolymers consisting of high molecular weight polysaccharides known as viscosity builders, gelification agents and stabilizers of food systems.

Several hydrocolloids such as gum arabic (acacia), tragacanth, xanthan and certain modified gums have been mentioned as food additives having special functions such as: "retardation of precipitation of dispersed solid particles and coalescence of oil droplets". The role of these gums as emulsifiers remained somewhat obscure. The present review is an attempt to bring the relevant studies together and to throw some light on the functionalities of the gums as surface active agents and food emulsifiers. In addition, some recent results obtained in our laboratory are discussed.

Gum arabic is compared to colloidal microcrystal line- cellulose (M CC) and galactomannans (recent results) in view of their abihty to reduce surface tensions, interfacial tensions and to stabilize oil in water emulsions via the 'steric' and 'mechanical' stabilization mechanisms.

It is demonstrated that while gum arabic adsorbs strongly and effectively onto the oil droplets via its proteinaceous moieties, guar gum and locust bean gum (LBG) adsorb weakly and for the most part only "precipitate" on the oil surface, and form birefringent layers of the polymer oriented with its hydrophobic mannose backbone facing the oil. The stabilization with MCC is claimed to be achieved via adsorption of solid particles on the oil droplets (mechanical stabilization).

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