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. © 2006 Ingenta.