Fining involves the addition of suitable substances to the freshly fermented wine to bind unwanted suspended matter through chemical reactions and/or adsorption, which can have negative effects on colour and taste. These are electrically charged. Either negatively charged like yeasts and tannins or positively charged like proteins and gelatine. The fining agents must be oppositely charged in order to bind the lees particles. They are added in dissolved form and form insoluble flakes with the unwanted wine ingredients, which sink to the bottom.
History
The Romans were already aware of the effect of beaten egg whites in winemaking in ancient times. In the Middle Ages, there were some questionable methods (or wine adulterations); for example, "colour and flavour improvement" with bovine 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, still cow-warm milk. It was also known that certain substances such as isinglass, gelatine, Spanish earth (kaolin earth) and coal bind the suspended particles in the wine.
Mode of action
The fining process ultimately achieves several effects. Above all, the natural settling of lees is significantly accelerated. It also removes substances bound in the wine that can lead to turbidity or negative impairment after bottling. In addition, the removal of filtration-inhibiting substances facilitates any subsequent filtration. Finally, wine defects are prevented at best or eliminated if they occur. A distinction can be made between the three groups of physico-chemical substances such as proteins, tannins, crystals (tartar) and heavy metals, biological substances such as yeasts and bacteria and other substances such as dust, filter material and cork abrasion. Fining works best with wines with a high acid content.
The optimum temperature for many fining agents is between 10 and 20 °Celsius. Microscopically small particles may not be captured by these methods; if necessary, these are subsequently removed using alternative techniques such as filtration, flotation or centrifugation. The wine is then separated from the fining lees by racking or decanting into another container. The various fining processes are sometimes also used in combination (see also the section on combination fining below).
Many producers, particularly in connection with organic viticulture or the production of organic wines, refrain from fining and also from filtering the wines in order to avoid the inevitable loss of flavours and aromas associated with these two processes. The fact that these wines are unfiltered is marketed accordingly. Fining residues are partly returned to the vineyard. Due to the cyanogen compounds, residues from the blue fining are excluded. The individual processes and the most commonly used technical terms for them are
blue fining
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 and black breakage. By adding yellow blood lye salt, copper and iron compounds are converted into an insoluble, blue substance that settles to 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 blue fining used to be called "Möslinger fining". It is also used to combat the wine defect frost flavour. The process is subject to authorisation and may only be carried out by authorised persons, as highly toxic substances such as hydrocyanic acid are formed in the presence of acids and when heated. If used incorrectly, the wine defect bitter almond note can occur. So-called complexing agents are used as an alternative.
Egg white fining
This is probably the oldest fining process and is used almost exclusively for red wines or wines with a high tannin content in order to reduce the tannin and thus make the wine milder or less harsh. Animal protein is added in the form of egg white; just one to three egg whites per hectolitre are sufficient. The active ingredient is albumin, which forms a fine-grained precipitate with the tannins (a similar effect used to be achieved with bovine blood). Although albumin does not attack the wine, it does have a slightly decolourising effect.
Protein stabilisation (heat stabilisation)
Protein turbidity is already caused at temperatures of 17 to 20 °Celsius, which is why this is also referred to as heat turbidity and the treatment as heat stabilisation. In larger quantities, a veil-like protein turbidity is caused in the wine. The protein content in the wine is determined by a so-called bento test. The heat-sensitive (thermolabile) proteins are removed from white wines using bentonite (see details there) and from red wines using freshly beaten egg white. The histamine content in red wine is also reduced in this way.
Colour stabilisation
A stabilising effect, especially in red wines, is achieved through targeted oxidation. This triggers polymerisation (agglomeration of substances) and causes anthocyanins and tannins to combine. When maturing in wooden barrels, a low level of oxygen contact is automatically provided by the wood pores. Targeted aeration is achieved through micro-oxygenation. The addition of oenological tannins accelerates polymerisation and promotes the formation of stable colour pigments. The best results are achieved immediately after malolactic fermentation or at the beginning of ageing in wooden barrels.
Gelatine fining
This form of fining is often carried out in combination with the fining agents activated charcoal, silica sol and tannins. See in detail under gelatine.
Tannin reduction
Too many colouring agents (so-called high colouring) and tannins can make a wine bitter and scratchy. Protein-containing substances (see egg white colouring) and PVPP (polyvinylpolypyrrolidone) are used to counteract this.
Isinglass fining
An older process (before the development of filtration technology) to make a wine bright before bottling. See in detail under the Hausen bubble.
Lees fining
Refreshing old and tired wines with an aged tone and also removing minor odour and flavour defects. A fresh lees (immediately after the end of fermentation) is used for this purpose.
Cold stabilisation
This process (also known as tartrate stabilisation) is carried out before bottling to precipitate out excess tartrate. The wine is cooled to around minus 4 °Celsius for a few days to a week. This is done using various methods such as room cooling, in tanks with cooling brine, cooling spirals or continuous flow coolers. The tartrate crystals quickly precipitate and sink to the bottom. Filtration may be required afterwards.
charcoal fining
This is carried out in both must and wine with activated charcoal to remove colour, odour or taste defects. This process, which has been known for a very long time, is an effective remedy for numerous wine faults. Charcoal has an extreme surface activity; just one gram of activated charcoal has an adsorption surface of up to 1,500 m². However, this can also have a negative effect on quality, because if too much is added, odours, flavours and colourings are removed to a serious extent. A precisely limited and targeted dosage is therefore required. The powder is stirred into the wine and takes some time to settle.
Combination fining
The mode of action of fining agents can be genuine chemical compounds or of a colloidal chemical nature, in which negatively and positively charged substances bind together. Increasingly, such substances are used in combination. Mixtures of casein and PVPP as well as gelatine and silica sol are very successful. Depending on the desired effect, the order in which they are added to the wine is important: silica sol (1) and gelatine (2) produce a pure clarification colouring, but vice versa a tannin correction and a clarification colouring.
Crystal stabilisation
Tartrate can be stabilised by preventing crystallisation using CMC (polysaccharide carboxymethylcellulose), which has been newly approved since 2009.
copper fining
Copper sulphate and copper citrate are used in an attempt to remove the dreaded wine defect "Böckser". This is usually followed by blue fining.
Self-clarification (natural fining)
This is the oldest form of wine clarification, which simply waits for the lees to settle without any intervention. This works particularly well with acidic wines, but can take up to several months. During red winemaking, tannins react with the dissolved protein and precipitate it. Self-clarification should not be confused with the degumming of the freshly pressed must.
Further information
A list of fining agents can be found under the heading " Wine-making agents". For information on the production of alcoholic beverages, see Champagne (sparkling wines), Distillation (distillates), Speciality wines, Spirits (types), Winemaking (wines and wine types) and Wine law (wine law issues).
