Collective clarification (also fine) for procedures to "beautify", "improve", "clean" or "preserve" a young wine. Degumming or clarification, on the other hand, are generally understood to be the processes used for grape must. In the past, fining mainly meant the clarification of the turbid matter of a wine after fermentation, which was also called flight fining. Today the term covers many different cellar-technical measures. By adding substances to freshly fermented wine, undesirable suspended solids are bound by chemical reactions and/or adsorption. All these substances are electrically charged. Either negative like yeasts and tannins or positive like proteins and gelatine. The fining agents must be oppositely charged in order to bind the cloudy particles to themselves. They are added in dissolved form and, together with the undesirable wine ingredients, form insoluble flakes that sink to the bottom.
The Romans already knew in ancient times about the effect of whipped protein in wine making. In the Middle Ages, there were numerous partly questionable methods (or wine adulterations); for example a "colour and taste improvement" with cow's blood. In the famous classic "Von Baw, Pfleg und Brauch des Weins" by the clergyman Johann Rasch (1540-1612), who worked in Vienna, some techniques are described in detail. Among other things, he explains how to restore a cloudy wine, namely by adding freshly milked milk still warm from the cow. It was also known that certain substances such as house bubble, gelatine, Spanish earth (kaolin clay) and coal bind the suspended particles in the wine.
Finally, several effects are achieved by the fining process. Above all, the natural settling of cloudy substances is considerably accelerated. Furthermore, substances bound in the wine are removed, which can lead to cloudiness or negative impairment after bottling. In addition, the removal of filtration inhibiting substances facilitates a possible subsequent filtration. Finally, wine defects are at best prevented at all or eliminated after their occurrence. A distinction can be made between the three groups of physico-chemical substances such as proteins, tannins, crystals(tartrates) and heavy metals, biological substances such as yeasts and bacteria and other substances such as dust, filter material and cork dust.
Beautification works best for wines with a high acidity. A temperature between 10 and 20 °Celsius is optimal for many fining agents. Microscopically smallest particles may not be detected by these methods. If necessary, they can be removed later by the alternative techniques of filtration, flotation or centrifugation. The wine is then separated from the fining lees by racking or decanting into another container. Some of the different fining methods are also used in combination (see also below under the paragraph combination fining).
Many producers, especially in connection with organic viticulture or the production of organic wines, refrain from the beautification and also from the filtration of the wines in order to avoid the loss of taste and aroma substances that inevitably accompanies these two processes. The fact of such unfiltered wines is marketed accordingly. Fining residues are partly returned to the vineyard. Due to the cyan compounds, the residues from the blue fining are excluded. The individual processes and the technical terms most frequently used for them are
Various iron compounds can get into the wine through fittings, pumps and filters (not made of stainless steel) and cause wine defects such as white breakage and black breakage. By adding yellow prussiate of potassium hydroxide, copper and iron compounds are converted into an insoluble blue substance that settles on the bottom and is then removed. The process was discovered in 1903 by the German wine chemist Dr. Wilhelm Möslinger (1856-1930), which is why the blue colouring was also called "Möslinger-Schönung" in former times. It is also used to combat the wine defect frosty taste.
The process is subject to approval and may only be carried out by authorised persons, as highly toxic substances such as hydrocyanic acid are formed especially in the presence of acids and when heated. Improper use can cause the serious, harmful wine defect bitter almond clay. So-called complexing agents are used as an alternative.
Probably the oldest fining process is used almost exclusively for red wines or wines with a high tannin content to reduce the tannin and thus make the wine milder or less rough. Animal protein in the form of egg white is added; one to three chicken egg whites per hectolitre are sufficient. The active ingredient is albumin, which forms a fine-grained precipitate with the tannins (a similar effect was previously achieved with cattle blood). Protein does not attack the wine, but has a slightly discolouring effect.
Protein turbidity is already caused at temperatures of 17 to 20 °Celsius, which is why this is also called heat turbidity and the treatment is called heat stabilization. In larger quantities a veil-like protein cloudiness is caused in the wine. The protein content of the wine is determined by a so-called bentotest. The heat-sensitive (thermolabile) protein substances are removed in white wines by means of bentonite (see there in detail) or in red wines with freshly beaten chicken egg white. The histamine content in red wine is also reduced in this way.
A stabilising effect, especially for red wines, is achieved by selective oxidation. This triggers polymerisation (agglomeration of substances) and causes anthocyanins and tannins to combine. A low oxygen contact is automatically given by the wood pores during the maturing in wooden barrels. A well-dosed aeration is achieved by micro-oxygenation. The addition of oenological tannins accelerates polymerisation and promotes the formation of stable colour pigments. The best results are achieved immediately after the biological acid decomposition or at the beginning of the wood barrel ageing process.
Too many colourings (so-called high colouring) and tannins can make a wine look bitter and scratchy. On the other hand, protein-containing substances (see egg whitening) and PVPP (polyvinylpolypyrrolidone) are used.
Refreshing of old and tired wines with an aging tone and also the elimination of minor odour and taste defects. A fresh tankard (immediately after the end of fermentation) is used for this purpose.
The process (also tartaric stabilisation) is carried out before bottling to precipitate excess tartar. The wine is cooled to about minus 4 °Celsius for a few days to a week. This is done by various methods such as room cooling, in tanks with cooling brine, cooling spirals or continuous flow coolers. The tartar crystals quickly precipitate and sink to the bottom. If necessary, filtration may have to be carried out afterwards.
Is carried out in both must and wine with activated carbon to eliminate defects in colour, odour or taste. This very old method is a proven remedy for numerous wine defects. Carbon has an extreme surface activity, already one gram of activated carbon has an adsorption surface of up to 1.500 m². However, the quality can also be negatively influenced, because if too much is added, odours, flavours and colourings are extracted to a serious extent. Therefore, a precisely limited and targeted dosing is necessary. The powder is stirred into the wine and the sedimentation takes some time.
The mode of action of fining agents can be true chemical compounds or colloidal chemical ones, in which negatively and positively charged substances bind together. Such substances are increasingly used in combination. Mixtures of casein and PVPP, as well as of gelatine and silica sol are very successful. Depending on the desired effect, the order of addition to the wine is important: silica sol (1) and gelatine (2) cause a pure clarification, but vice versa a tannin correction and clarification.
This is the oldest form of wine clarification, where the wine is simply left to settle without any intervention. This works particularly well with acidic wines, but can take up to several months. In red wine making, tannins react with the dissolved protein and precipitate it. Self clarification must not be confused with the degumming of the freshly pressed must.
A comprehensive list of possible fining agents can be found under Agents used in winemaking. Complete lists of the numerous vinification measures and cellar techniques, as well as the types of wine, sparkling wine and distillate regulated by wine law are contained under the heading Vinification. Comprehensive information on wine law can be found under the keyword wine law.