On the film-forming and emulsion-stabilizing properties of gum arabic: dilution and flocculation aspects

Physico-chemical factors relevant to the emulsifying and stabilizing properties of gum arabic arc discussed. Experimental information is presented relating to (i) the effect of extensive dilution of the aqueous phase on the surface viscosity at the planar oil-water interface and (ii) the effect of non-adsorbing polysaccharide on the emulsion stability. We conclude that the surface rheology of gum arabic films is relatively insensitive to dilution of the aqueous phase, although clear evidence is found for a small but significant reduction in the surface viscosity over a time-scale of the order of 100 h. We observe that addition of dextran to gum arabic emulsions at high ionic strength leads to enhanced instability with respect to creaming; the effect is attributed to depletion flocculation.