Fining is mainly aimed at improving the clarity and sensory features of wine. While various physical methods, such as centrifugation and filtration, can be applied to clarify juice and wine,the reduction or elimination of compounds responsible for wine instability or imbalance is often best achieved by using fining agents.

How to fine-tune your wine

Fining agents help remove undesirable elements or compounds to improve the quality of wine. Fining is not just used in wines for bottle preparation, in some cases there are more benefits from early fining rather than later in the life of a wine. Early fining is most important in the correction of obvious flaws, for example: harsh and unbalanced mouthfeel, off aromas and flavours caused by the wine’s reductive or oxidative state, and even the removal of microbial organisms. For the most part, early fining will allow the wine to age properly while limiting further treatments that could be needed prior to bottling.

Mechanism of action
The mechanisms of action in fining are diverse and depend on the nature of the fining agent. These interactions can be based on charge, formation of chemical bonds, and/or absorption or adsorption of compounds. When added to wine, fining agents usually form a colloidal dispersion. Depending on the electrical charge of the fining agent molecules when dispersed in wine, the colloids may be classified as being either electropositive (e.g. protein fining agents such as gelatins) or electronegative (e.g. tannin, bentonite, silica sol).
These interactions lead to the formation of two important processes that need to happen in sequence: first, flocculation (the aggregation of two or more macromolecules) then sedimentation (when the flocculated materials settle to the bottom of the tank).

Co-fining (flocculation aids)
When fining white, rosé or other low tannin wines, some protein-based fining agents, particularly gelatin, which have a positive electric charge, require the addition of negatively charged colloids in order to ensure complete flocculation and, eventually, precipitation. Such negatively charged flocculation aids include: tannin, silica sol and bentonite.

Testing and evaluating Fining Agents
Trials are essential for evaluating the efficacy of a treatment. Fining agents and concentration ranges used in a trial can be selected on the basis of the change that is desired in the wine. It is important to test several rates and select the lowest dosage needed to achieve the desired effect in order to avoid over-fining. For fining trials intended to modify the organoleptic status of the product, the most important test of all is a properly conducted sensory evaluation of the fined samples against an untreated control. Additionally, there are several tests that winemakers can use to cross reference with their sensory evaluation.

Things to consider when using Fining Agents
All fining agents must be added very evenly to the volume of wine (or must) that is being treated. If possible, incorporate fining agents using a Venturi tube or dosing pump during pump-over or racking.
• Avoid prolonged use of mechanical stirrers, which can delay the flocculation process.
• When flocculation aids are used, the following order of addition should be used: tannin must always be added before gelatin, if possible one day earlier; bentonite and silica sol should be added before protein fining agents when treating free run must and wine, and after protein fining agents when treating pressed must and wine.
• If there is a risk of over-fining with protein fining agents, always end the sequence with bentonite.
• Always allow one or two hours to elapse between additions.
• Fining solutions must be used immediately after preparation (allowing only for swelling times, if applicable).
• If solutions need to be used over two or more days, add 2 g/L of potassium metabisulfite to the solution to inhibit microbial growth. Never store prepared solutions for more than one week.
• Protein fining agents should not remain in the wine for more than 10 - 15 days in the case of gelatin, casein and egg albumin, and 3 - 4 weeks in the case of isinglass.
• Avoid temperature differentials in tanks to which fining agents have been added - these create convective movements within the tank that delay the settling of lees.
• Protein fining agents work best at low temperatures: 10°C for gelatin and up to 5°C for isinglass.
• Bentonite works best at temperatures higher than 10°C
• Chitosan must be in suspension for 1 hour or more to optimize treatment.

Allergen-Free Fining Agents
Enartis has created a line of clarifying and fining agents that are free from allergenic proteins and can be used as alternatives to egg albumin, casein or potassium caseinate and are suitable for the production of wines to be consumed by vegetarians and vegans.

If you want to know more about fining agents, hiw to use them and how to run clarification trials, please open the pdf.

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