Le cellar practices are a fundamental step in the production of wine in order to improve its stability and organoleptic qualities. This article explores the wine clarification and in particular two are analysed clarification materials: l'albumin and the jelly. The choice of clarification material must be made according to the desired result, the characteristics of the wines to be treated and the technological constraints.

Wine clarification: how is it done?

Clarification is a practice carried out at low temperature that consists of adding substances that form heavy aggregates with the particles to be removed, which then settle at the bottom of the container. The substances added can be organic (animal gelatine, vegetable gelatine, albumin, isinglass) or inorganic (aluminium sulphate, bentonite, potassium caseinate, etc.) or a combination of these. In practice, these clarification aids bind to the particles suspended making them heavier and thus they precipitate or filter out more easily.

Each type of wine requires a customised approach to clarification, based on the desired characteristics of the finished product and the applicable regulations on additives and production methods. The choice of clarification methods and adjuvants can significantly influence the aromatic profile, taste and long-term stability of the wine.

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Albumina

Widely used with the best quality wines for its ability to eliminate astringency and bitterness in red wine. It also refines the structure, corrects any oxidised hints and respects the typicality of the grape varieties used and the wine obtained from them. Commercially, it is a powder to be rehydrated with cold water because it is sensitive to heat. Another property of albumin is the low reduction of polyphenols even at high doses compared to bentonite. However, dosages are very limited compared to the other methods. Today, powdered albumin of excellent quality is used; historically, cellarers used an egg white with a pinch of sodium chloride.

Jelly

The value of the action performed by gelatine in the clarification process is directly proportional to its surface charge. The higher the surface charge of gelatine, the broader its range of action. This means that gelatine acts on all types of tannins by refining their properties and maintaining their balance. The lower the surface charge of gelatine, the lower its spectrum of action. This means that gelatine only acts on the most reactive and aggressive tannins and therefore also plays a balancing role in disharmonised wines. From this we can see that a gelatine with a high surface charge is useful in old, structured wines, while a gelatine with a low surface charge is perfect for young, astringent wines.

Animal gelatine

For years it was the most widely used material for clarification, only to be 'feared' during the mad cow years. Currently, pig skin is mainly used to obtain it. It is presented commercially as a thin transparent sheet that is more or less pure. It is used like isinglass to make cakes: it is left to soak in cold water to swell and soften, then dissolved in a lukewarm liquid, mostly water.

Vegetable gelatine

Obtained from peas, it is even less used than animal gelatine. Its action and mode of use are similar to animal gelatine, with the difference that the resulting wines are softer because it binds to the more astringent tannins and produces less lees.

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Wine clarification: questions and answers

When to clarify wine?

Clarification always takes place after fermentation.

At what temperature should wine clarification be carried out?

The optimum temperature for wine clarification varies depending on the clarification method used and the type of wine to be made. In general, it can be said that clarification usually takes place at relatively low temperatures to favour the stability of the wine and prevent any undesirable reactions. In particular:

  • white and rosé winestemperatures ranging from about 5 °C to 15 °C;
  • red winestemperatures ranging slightly from 10 °C to 20 °C.

The exact temperature depends on both the structure of the wine and the clarifying substance used.

How to prepare bentonite for wine clarification?

Bentonite is one of the most widely used clarifying substances in wine production. It is a type of clay that has an excellent ability to bind proteins and other suspended particles in wine, facilitating their precipitation and removing them from the liquid. Preparing bentonite for wine clarification requires some specific steps to ensure that it is effective in removing suspended particles without compromising the quality of the wine:

  1. water preparationbentonite is hydrated with pure water at room temperature or slightly warmer at a ratio of 1:5 to 1:10 (500 g to 1 kg water is used for 100 g bentonite);
  2. mixingbentonite is slowly poured into the water, stirring continuously to avoid the formation of lumps and to obtain a homogeneous mixture;
  3. restIt is left to rest for a few hours in order to promote proper hydration and activate it;
  4. verificationCheck that the consistency is right, i.e. creamy, and if it is too hard, add water (this is why it is advisable to start with a lower proportion of water and add it later if you are not sure).

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