Physical-mechanical process (including filtration, filtering and filtering) for the separation or cleaning of substances such as liquids or gases using technical filter devices. Different filtration processes are a common process in the winemaking, Already in the antiquity there were with the Egyptians. Sumerians and Romans a technique in which wine was filtered using cloths or similar materials. In the Middle Ages, the pieces of muslin that acted as a filter were used to add flavoring Spices filtered out of the wine. This piece of fabric was referred to as "Manica Hippocratis" (sleeves of Hippocrates).
In today's viticulture, filtration mainly affects grape and young wine, but also for the purpose of air and disinfection water, The purpose of this process is to remove unwanted substances and thus to stabilize or sterilize the grape must or wine. This is usually done in several steps. First, the ones that were created during the pressing process are quite large lees (Pulp) removed from the must (see under degumming and clarify ). Only then is the so-called filter maturity of the wine achieved as a prerequisite for the respective type of filtration. This means that the wine must not be too cloudy. The next step is to remove microorganisms how yeasts and bacteria,
Filters not only hold back those particles that are (as you might assume) larger than the filter pore size. Because that's just one of the effects. Other mechanisms include particle inertia, diffusion effects (thermal movement of particles), electrostatics adsorptive Effect or blocking effect. For this reason, particles that are much smaller than the pore size of the filter are always separated. In any case, filter pore sizes of ≤ 1 µm (millionths of a meter) are required (human hair approx. 40 µm).
Filtration can be carried out several times in different stages of winemaking, especially after Press (Most), after the fermentation as well as immediately before or at the bottling, Usually, several of the methods listed below are carried out in combination. However, filtering always means a more or less strong mechanical load on the wine, and (too high) losses of flavorings or carbonic acid result, so this method should be used with care. With improper or too sharp application, this can lead to filter shock to lead. Many producers therefore largely do without filtration.
Starting from the United States For marketing reasons, the label "Europe" has increased in recent years unfiltriert “(Or similar) find. The alternative to filtration is racking (Moving) from one container to another, which is certainly much gentler, but much more complex. The Beaujolais Nouveau is basically unfiltered wine. For wines with longer periods barrel aging Storage automatically results in better stability. Unfiltered wines represent a much greater extent depot (Sediment). In principle, no filtration is carried out for special wines such as "sur lie" (see under lees ).
The unfiltered mixture of a liquid and finely divided solids is called a suspension, and the filtered product is called filtrate. Depending on the filter, the particles are either based on the size (sieve effect) and / or on the basis adsorptive (Electrostatic) effect eliminated. There are a number of different filtration techniques, depending on the size of the company, technical equipment and the type of wine desired.
The filtration mechanisms or application techniques are divided into the following basic principles:
A distinction is made between surface or membrane filtration and deep filtration according to the location of the sludge retention. During surface filtration, the solids filtered off form a layer on the filter medium, the filter cake, With deep-bed filtration, they are held in the depth (inside) of the filter medium. There are the variants precoat filtration, layer filtration and depth filter modules / candles. According to the liquid flow, a distinction is made between static and dynamic filtration .
Static filtration (also frontal or dead-end filtration): The direction of flow of the liquid is vertical from top to bottom (vertical) through the filter area. All particles are retained either on the surface (surface or membrane filtration) or in the depth of the filter medium (depth filtration).
Dynamic filtration : The liquid is not passed vertically through the filter medium, but parallel or across a membrane surface. There is no dynamic depth filtration.
A sharp filtration can also be used fractionate of wine. Various substances such as alcohol and flavorings separated and put together to a "new wine". However, this application is prohibited within the EU or on very few applications such as alcohol reduction restricted, but in the New world usual (see under Spinning cone column ).
The most important of the many forms with the most varied filter techniques and in the most varied variants, which are often used in combination, are:
Membrane filtration : The static MF is mainly used for sterilization. This requirement is met if all potentially harmful microorganisms can be removed. Large surfaces are required because of the low turbidity absorption capacity, which is why the membranes are mostly folded (pleated) like an accordion.
Cross-flow filtration (also cross-flow filtration or tangential flow filtration): It is a dynamic form of filtration. The name is derived from the direction of flow of the liquid. This is led across a membrane surface (crossflow). This allows the size range of the particles to be specifically selected. Depending on the particle size of the solids to be separated, micro-filtration (0.5 to 0.1 µm), ultra-filtration (0.1 to 0.01 µm) and nano-filtration (0.01 to 0.001) are used µm) differentiated. At sizes from 1 to 0.1 nm (billionths of a meter) one speaks of reverse osmosis (see under osmosis ).
The wine is pumped through the membrane at high speed. The filter cartridge consists of many asymmetrically constructed, hollow membrane fibers made of plastic in a vertically arranged filter housing. There are none on newer models filter aids more necessary. The wine is repeatedly pumped through these hollow fibers in the cycle, a small, filtered part flows continuously sideways out of the housing, the larger part remains in circulation. The advantage of this technique is that clarification (compared to all other techniques, where at least two work steps are necessary) is carried out in a single work step and filtration is possible even with a very high degree of turbidity, such as with a still cloudy young wine.
Alluvial filtration : In the case of the static depth filtration form, filter aids such as diatomaceous. perlite u. cellulose as well as powdered resins as ion exchanger used. These are first suspended (dissolved) in a liquid and then washed onto the filter holder. As soon as a sufficiently thick filter cake has built up, which then acts as the actual filter, the liquid to be filtered is switched over. This means that the smallest undissolved particles can be removed to a large extent. In addition, depending on the aids, too adsorptive Effects are achieved.
Layer Filtration : The static deep filtration form is mainly used in Central Europe; in Austria around 90%. In contrast to the precoat (where only one filter cake is built), there is a prefabricated filter bed. Depending on the application, this consists of a special mixture of filter aids such as cellulose, diatomaceous earth and / or pearlite as well resins, Depending on the mixture, there are special filter properties. The layer, which is only 3 to 5 mm thick, results in a labyrinthine, close-meshed room sieve with the finest, countlessly branched channels. The wine flows through these channels relatively slowly. The mode of action results from a mechanical sieving effect and an additional adsorptive component.
Drum vacuum filtration (vacuum rotary filter filtration): In this form, a rotating drum is mounted in a tub, which is surrounded by a fine-meshed stainless steel mesh. A mixture of water and filter aid (diatomaceous earth or perlite) is placed in the tub. This is only suitable for must trub, not for wine.
The filtration residues (lees, yeasts) are returned to the nutrient cycle in the vineyard because organic matter is predominantly nutrient-rich with a high level nitrogen content having. Larger amounts of filter aids reduce the nutrient content. However, since it is difficult to spread large areas when fresh, the residues are usually mixed beforehand with straw, bark, chopped wood or rapecomposted, Excluded from this is the fining slurry that occurs in the case of blue finishes, which must be disposed of due to the cyan compounds contained therein (see under beautiful ).
Possible alternatives to filtration using various mechanical devices are flotation and centrifugation, Other procedures are under the keyword beautiful described. Complete lists of the numerous cellar techniques, as well as the wine, sparkling wine and distillate types regulated by wine law are under the keyword winemaking contain. Comprehensive information on wine law is available at wine law,