Surface activity and emulsifying behaviour of some Acacia gums

The surface and emulsifying properties of six Acacia gum samples with nitrogen contents in the range 0.09-7.5% have been investigated at neutral pH. Samples which give a relatively rapid lowering of the tension at the n-hexadecane-water interface produce oil-in-water emulsions with small droplets and good stability with respect to creaming. Although the nitrogen content of these gums shows a reasonable correlation with the limiting long-time surface activity, there is no simple relationship between nitrogen content and emulsifying behaviour. It is suggested that the variability in the emulsifying properties of the gum samples from different Acacia species is dependent not only on their total protein ( or polypeptide) content but also on the distribution of the protein/peptide between the low-and high-molecular-weight fractions, and on the molecular accessibility of the protein/peptide for adsorption.