The fact that for both series of emulsions, W and R, the optimum percentage of wine addition was 20% (v/v) could be attributed to the similar ethanol content of the two wines. It is generally accepted that ethanol often acts as co-surfactant reinforcing the films that surround the oil droplets [12] and [18]. Previous studies on O/W emulsions that contained proteins in the aqueous phase have suggested that the addition of ethanol at 5–20% (v/v) interacts with the presence of electrolytes creating a stronger structure around the droplets [18]. The mechanism has been characterized as non specific and has been linked to the decrease of the dielectric constant of the matrix. In this way the water soluble constituents, like proteins and salts which are found in wine, are driven towards the droplet interfaces making the films more compact either through electrostatic forces or by diminishing the stereochemical obstructions [18]. This has been observed only for limited ethanol and electrolyte concentrations because at higher percentages phase separation is most likely to occur. The same studies have shown that the higher the ethanol content in such emulsions, the lower their viscosity values and the higher their droplet sizes [18] and [19], exactly as presented in Table 3 of the present study for increasing wine concentration.