Passage of liquid through a semipermeable partition wall, for example clay or parchment paper or even cell walls in living organisms, which separates two liquids of different concentration. Osmosis also plays a major role in metabolism. The discovery of the phenomenon succeeded the Danish chemist Jacobus Hoff (1852-1911) in 1874. This partition (also diaphragm ) is permeable by a corresponding pore size only for the molecules of a liquid (eg., Water), but not for the solute (eg sugar molecules). There is diffusion (flowing apart) toward the concentrated solution. Substituting a container 1 (with a semi-permeable outer wall) with highly concentrated solution (eg sugar water) in a container-2 with pure water, so that an equal level of liquid in both containers, then migrate the water molecules to the container-1 ,
The water molecules are "sucked in", so to speak, because there are fewer water molecules. The level in container-1 increases (limit) until the so-called osmotic pressure in container-2 is equal to the hydrostatic pressure (pressure of a quiescent liquid) in container-1. For pure liquids such as water and alcohol However, the flow of molecules can be done in one direction or the other depending on the type of partition. Differences in molecular size have long been used for various applications. These include seawater desalination, the concentration of fruit juices and dairy products, as well as the cleaning of liquids (eg waste water). The larger red particles shown in the picture can not penetrate the pores of the membrane, whereas the blue ones do.
In reverse osmosis (also inverse osmosis), both liquids must also be separated by a semi-permeable membrane. Now the side with the highly concentrated liquid is pressurized (which must be higher than the natural osmotic pressure), on the other side is water. Only the smaller water molecules can pass through the membrane. The higher the pressure, the more water flows against the osmotic potential on the side with the lower osmotic potential, the chamber with the water. The osmosis is thus reversed, from which the name derives.
Within the EU, the procedure is in order enriching at the grape authorized. The proportion of sugar increased by withdrawal of water. For wine, there is an application concerning alcohol reduction allowed. Other applications such as removal of undesirable substances (volatile phenols after Brettanomyces. corked ) as well as from residual sugar may only be possible with exemptions.
The (not undisputed) reverse osmosis is still in the experimental stage and used only occasionally by larger wineries. In addition to osmosis, there are other ways to concentrate, namely, as the oldest form, the drying of grapes or the exploitation of different boiling or freezing points by different techniques of concentration like, for example ion exchange,
Complete listings of the numerous vinification measures and cellar techniques, as well as the various wine-regulated wine, sparkling wine and distillate types are under the keyword winemaking contain. Comprehensive information on wine law is available under the keyword wine law,