Comparison of the Properties of Vegetable Oil/Water and n-Tetradecane/Water Emulsions Stabilized by α-Lactalbumin or β-Casein

Abstract

The properties of a refined vegetable oil (a mixture of rape and sunflower oils) and of n-tetradecane emulsions in the presence of proteins, i.e. α-lactalbumin and β-casein, were investigated. These proteins differ in their surface affinity, size and structure, and were therefore expected to show some differences in adsorption at the oil droplet/water interface. The oil samples (0.5–5.0 ml in 100 ml water) were emulsified mechanically in the presence of 1.0–5.0 mg of the protein. The stability of the emulsions was investigated via the effective diameter and multimodal size distribution of the droplets using the dynamic light-scattering technique. In addition, the zeta potentials of the emulsions were measured and found to be negative and in the range −5 mV to −20 mV in all systems. Multimodal size distribution analysis showed that soon after preparation the emulsions were quite well monodispersed. In general, α-lactalbumin appeared to be a good or even better emulsifier than β-casein for both kinds of emulsion (vegetable oil and n-tetradecane in water). Moreover, it appeared that for stability of these emulsions, the optimal ratio of oil and protein content was very important