Ouzo effect
As a louche effect (French louche, opaque ',' suspect ',' offensive ' ) refers to the milky haze anishaltiger clear liquors such Absinthe, Pastis, Sambuca, Ouzo, Mastika, Raki or Arak, when diluted with water or very strong be cooled. Using the louche effect of Anisgehalt different beverages can be compared: the more turbid the liquid is at a certain mixing ratio, the more anise is contained in the distillate.
Basics
Cause of the louche effect is the content of essential oils especially from the anise seed as well as possibly other aromatic plants such as mint, coriander, and lemon balm. These oils, which contain lots of anethole in Anisschnäpsen, soluble in alcohol, but not or only slightly in water. Water as hydrophilic ( polar ) material and the contents of the hydrophobic essential oils rather form an oil- in-water emulsion, are surrounded in the hydrophobic oil particles from water. The droplet diameter is placed at about a micrometer. At the interfaces between water and oil droplets, the light is scattered, causing the milky white turbidity. So you do not based on a chemical reaction, but is physical in nature (see also Tyndall effect).
The louche effect can be cause by strong cooling of anise liquor without adding water. At low temperatures, the solvent power of alcohol decreases, and it also any oil droplets.
Ouzo Effect
Although the louche effect has long been known as such already has been established since 2003, the name Ouzo effect for the spontaneous emulsion formation in a ternary system of immiscible and miscible fluids without the supply of energy or surface-active substances in the scientific world. These microemulsions form spontaneously and are extremely stable. By addition of the hydrophilic solvent, the hydrophobic phase is supersaturated, which leads to the formation of small aggregates or droplets. The formation of such an emulsion is usually observed by dynamic light scattering. First, there is a homogeneous nucleation, which leads to a uniform dispersion. The aggregates grow by droplets or Ostwald ripening, at a diameter of hundreds of nanometers to several micrometers and do not coalesce. The size distribution is very uniform ( monodisperse). The final size can not be influenced by the pH, ionic strength, or by stirring, but is only on the ratio of the solute to the solvent dependent. Whereby the growth is limited, is not yet fully understood. However, the whole process is carried out only within a narrow concentration window. The metastable dispersions occur only between the spinodal and the binodal of the phase diagram of the mixture in question.
Application
The ouzo effect is for a variety of applications of importance, since a wide variety of materials such as polymers, oils, greases or drugs in aqueous solution by this effect can be easily emulsify. These emulsions have a high stability and is free from emulsifiers. Therefore, they are of particular interest to the food industry, but also for the cosmetic or pharmaceutical industry. In addition, a wide range of particles in the submicron to nanotechnology and biotechnology are generated. Due to changes in the concentration or the combination of different solutes can be synthesized easily nanocapsules or other nanoparticles.