The effect of emulsifier concentration on the rheological properties of acacia emulsions

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The effect of potassium arabate concentration on the rheological properties of liquid paraffin emulsions has been examined over a range of emulsifier concentrations and volume fractions. The emulsions were of small particle size. Aggregation of the emulsions occurred when the volume fraction (ø) was in the region of 0·33–0·43, the exact value of ø depending on the emulsifier concentration. The aggregated emulsions demonstrated irreversible shear thinning and hysteresis loops were obtained. The aggregation only occurred during the emulsification process and was due to a macro-molecular bridging mechanism. The emulsifier concentration influenced aggregation and thereby influenced the rheological properties of the emulsions by two opposing mechanisms. It decreased the volume fraction at which aggregation first occurred (øagg), through its influence on particle size, but increased øagg through its effect on the degree of contraction of the acacia molecule.