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Collective term for various physical processes for the removal of particles (lees) from the young wine with technical equipment with the help of filters and filter material (some alternatives are Flotation and Centrifuge ). Even in ancient times there were the Egyptians, Sumerians and Romans, a technique explained in the wine with cloth or similar material (filtered) was. In the Middle Ages by means of the so-called "sleeve of Hippocrates" was - a piece of muslin fabric - the added spices filtered out of the wine (see below Flavoring ). The foundations for today's conventional filtration by means of technical devices were already in the early 20th Century developed. It can, depending on filter size / type, or gross and microscopically tiny particles are separated from the wine.
The pore size of the filter is moving in the range of 20 thousandths of a millimeter (20 microns) and 0.45 mm (the diameter of a human hair is 40 microns). Filtered in order to make the wine blank, or microorganisms such as Bacteria or Yeasts to remove and thus to stabilize the wine. It is almost always a complementary measure, previously made a preclarification and Fine In order to remove even the roughest parts of the wine. This sets the stage - the so-called filter ripening of the wine (he may not for that of filtration to be cloudy).
Filters act as a sieve through their pores and are varying degrees depending on the material effectively. The liquid drains or is pumped through the filter, the sediment particles are held back. A distinction is made between mechanical (material must be retained because of their size) and Adsorption Effect (due to different electric charge of filter fibers and sediment particles are attracted and adhere latter class). Some techniques to reach both. Today are mainly used layers or membrane filters. Filtering means always a more or less severe mechanical stress of the wine, it can also result (excessive) losses of aroma substances or carbon dioxide, so this method must be used carefully.
The method is therefore not without controversy, and there are passionate supporters and determined opponents. Based on the United States can be for marketing reasons on the bottle label in Europe in recent years more and the message " unfiltered "(Or spirit) found. The alternative to filtration is the Racking (Move) from one container to another, which is certainly far more gentle, but is much more complicated. The famous Beaujolais Nouveau is generally the case unfiltered wine. For wines with a longer barrel in results from the storage automatically better stability. Unfiltered wines are also a much greater extent a deposit (lees). In case of special wines such as "sur lie" should in principle be no filtration (see also under Lees ).
Cross-flow filtration: This also ultra-filtration and tangential flow filtration technique called a special type of membrane filtration (see below). The used filter cartridge contains a small space, a maximum membrane surface. This consists of many asymmetrically constructed, hollow membrane fibers made of plastic in a vertically arranged filter housing. The wine is pumped in circulation again and again by these hollow fibers, a small (filtered) part flows in each case sideways out of the housing, the greater part remains in circulation. The name comes about because the membrane tangential (cross flow = cross-flow) is flown. The advantage of this technique is that the clarification made (compared to all other techniques, where at least two operations are necessary) in a single operation (the wine is then filling ripe) and a filtration even with very strong turbidity (for example, still fermenting over young wine) is possible. In addition, no filter aids are necessary.
Diatomaceous earth filtration: This traditional technique is now used mostly for pre-filtration. There are so-called precoat, plates and boiler-filter. In the filtration of the filter elements are made of fine steel mesh (mesh dress), the so-called sieve. The wine will flow with Diatomaceous (Fossil shells and housing of the diatoms) was added, the diatomaceous earth forms on the screen surfaces together with the sediment particles and a filter cake is then separated. As the diatomaceous sediment particles by the relatively rapid decomposition, must constantly fresh diatomaceous earth is added.
Membrane filtration: This is a so-called surface or sieve filtration, wherein a used (compared to layers filters) relatively thin, single plastic membrane with defined pore sizes (smaller than the sludge particles to be removed). The membrane must be a so-called pre-filter upstream. The absorption capacity is relative to the filtration layers is relatively low. In contrast to this, however, (it is the filter from 1.2 to 0.2 microns) by a correspondingly smallest pore size can be ensured that yeasts and bacteria are retained.
Layers filtration: This is a so-called depth filtration, which is applied in Central Europe for the most part. In Austria it is 90% with the overwhelming process. The sieve plates pressed between filter layer is formed of several tightly pressed sheets. This yields (relative to the membrane filters) a relatively thick layer (chamber). The material consists of cellulose, synthetic fibers, diatomaceous earth or perlite (volcanic rock with crystal-like structure). The thick layer results in a maze-like, very tightly woven with the finest Raumsieb, countless branching channels. The wine flows through these channels is relatively slow, the sediment particles are retained mechanically in the channels, but also bound by adsorption.
Drum Vacuum Filtration: This is a rotating filter, which operate on the principle of diatomaceous earth filtration. Before the start of the filtration on the filter cloth, a thick layer (6-10 cm) of washed diatomaceous earth or perlite (volcanic igneous rock) through which the wine is drawn. This technique can also be applied when Most. The Trubschicht is then scraped off continuously.