Fining and Stabilization in Wine: Processing Aids, Disclosure, and Vegan Claims

Wine Additives Series - Part 4 of 5

European wine labels changed materially, and the change was overdue.

Since December 2023, wine sold under the applicable European Union rules has carried mandatory ingredient and nutritional information, applying broadly from the 2024 harvest, with qualifying earlier stock continuing under transitional provisions. Much of the detail can be delivered electronically, usually through a QR code, while certain mandatory information still has to remain physically associated with the bottle.

A consumer can now see acidity regulators, stabilizers, preservatives, concentrated must, gum arabic, and other materials when they remain in the finished wine and fall within the disclosure rules.

That is real progress, and I support it.

It will also disappoint some of the people who campaigned hardest for ingredient transparency, because much of what happens in a cellar remains legally invisible by design.

Not by loophole.

By definition.

Why Most Cellar Products Are Not Ingredients

A processing aid is used during production and is not intended to remain in the finished wine. It performs a function and is then settled, racked, or filtered out. Trace residues can persist, but the material is not considered part of the composition of what you drink in the same way as an ingredient that remains in the wine.

That distinction covers much of the fining bench.

Bentonite, egg albumin, gelatin, casein, isinglass, pea protein, potato protein, PVPP, silica products, and activated charcoal may all be used during production and subsequently removed.

So a wine can undergo several fining treatments and still carry a relatively short ingredient list.

The ingredient list can be accurate and still fail to tell you everything that happened in the cellar.

This is the honest limit of ingredient disclosure, and pretending otherwise damages the credibility of the system rather than improving it.

The Fining Bench

Bentonite is a clay and one of the workhorses of white and rose wine production.

Grape proteins can be heat-unstable. A wine shipped through a warm supply chain without adequate protein stabilization may eventually develop a haze in the bottle. The haze is usually harmless, but consumers can easily interpret it as spoilage.

A heat-stability test helps determine the amount of bentonite required.

Guessing costs you either clarity or aroma.

Bentonite is not perfectly selective. It removes unstable proteins, but it can also remove desirable aromatic compounds associated with those proteins. Every gram used beyond what the wine actually requires is therefore a gram spent stripping the wine.

Over-fined Sauvignon Blanc is a specific disappointment. The varietal signature begins to thin, the mid-palate becomes hollow, and what remains may be technically stable but aromatically ordinary.

Egg albumin has been used for centuries to soften harsh tannin in red wine. It tends to act more selectively on coarse and aggressive tannin fractions, which is one reason it remains relevant in serious red-wine production.

Casein can help address browning and oxidative character in whites.

Gelatin and isinglass are used for clarification.

PVPP is particularly useful for removing oxidized and bitter phenolic material and can be used to manage pinking in white wines.

Plant proteins derived from pea and potato increasingly replace animal-derived fining materials.

The reason is partly allergen management and partly market access.

Animal-derived fining can disqualify a wine from a vegan certification program or from a retailer's vegan standard even when the fining material itself has been removed before bottling.

There is no single worldwide statutory definition of "vegan wine," so a producer making a vegan claim has to understand the certification or market standard being targeted before conducting the fining trial, not after the wine has already been treated.

Activated Charcoal: The Blunt Instrument

Activated charcoal sits at the aggressive end of the fining spectrum.

It can remove serious color, odor, or flavor defects, including certain smoke-related compounds and microbial off-aromas.

It can also remove a great deal of desirable wine character at the same time.

A heavily charcoal-treated white wine is a recognizable experience. The texture may still be correct, but the aromatic life of the wine feels distant, as though you were tasting the fruit through glass.

The defect remains.

Unfortunately, much of what was standing next to it may have left as well.

Stabilization and the Tells

Stabilization is a different discipline, and unlike most fining materials, several stabilizing products remain in the wine.

Gum Arabic

Gum Arabic can soften astringency, smooth a finish, and help with colloidal stability.

Used on a wine that already has structure, it can polish.

Used on a thin wine, it can produce a slickness through the mid-palate that never develops into flavor.

Real texture from glycerol, lees, or mannoproteins normally carries something aromatic or structural with it.

Gum Arabic can create polish without adding that same underlying substance.

Tartrate Stability

Tartrate stability can be managed through cold stabilization or by using authorized materials such as metatartaric acid, carboxymethyl cellulose, mannoproteins, or potassium polyaspartate.

The crystals these treatments prevent are harmless.

They are mainly prevented because consumers often mistake them for broken glass or a product defect and return the bottle.

Metatartaric acid has a limited working life and loses effectiveness with heat, which can make it a poor choice for wine moving through a warm supply chain.

Carboxymethyl cellulose is durable in many white wines but requires careful use because wine composition affects how well it performs.

Choosing among these tools is therefore not only a cellar decision.

It can also be a shipping and market decision.

Ascorbic Acid

Ascorbic acid is an antioxidant with a condition attached.

It reacts quickly with dissolved oxygen, but it normally requires adequate free sulfur dioxide alongside it because one of the products formed during its oxidation is hydrogen peroxide.

Used without sufficient sulfur protection, ascorbic acid can eventually contribute to the oxidation it was intended to prevent.

It is not a replacement for sulfur dioxide.

It is a supplement to it.

Microbial Control Before Bottling

Several tools matter when controlling microorganisms before bottling, and each works differently.

Sulfur Dioxide

Sulfur dioxide provides both antioxidant and antimicrobial protection, but its effectiveness depends heavily on pH.

That is why sulfur management cannot be separated from acid management.

Sterile Filtration

Sterile filtration removes microorganisms mechanically.

Some producers avoid it because they believe it can affect texture or aromatic expression, but declining filtration also means accepting the microbial risk that filtration would otherwise remove.

Dimethyl Dicarbonate

Dimethyl dicarbonate, usually referred to as DMDC, sounds considerably more alarming than it behaves in practice.

It can reduce viable yeast and other microorganisms shortly before bottling and then decomposes rather than remaining indefinitely as an active preservative.

It is precise and useful where refermentation risk is real, but it has to be applied accurately and within the authorized conditions.

Potassium Sorbate

Potassium sorbate is a material to watch carefully.

It inhibits yeast growth and helps prevent refermentation, but it does not provide the same protection against lactic acid bacteria.

That asymmetry can create a problem.

If certain lactic acid bacteria metabolize sorbate, they can produce compounds associated with the unmistakable smell of crushed geranium leaves.

It is one of the easiest faults in commercial wine to recognize once you have learned it.

It is also highly preventable.

Lysozyme and Allergen Rules

Lysozyme is an authorized treating material used to control certain lactic acid bacteria and manage malolactic activity.

It is derived from egg white.

This matters because allergen-disclosure rules are not identical worldwide.

In the European Union, applicable wine allergen rules can require disclosure of egg-derived allergens when the regulatory conditions for declaration are met.

In the United States, TTB-regulated alcoholic beverages currently operate differently. Major food-allergen disclosure remains voluntary under the existing interim framework, while proposed mandatory requirements should not be treated as current final law until they actually become effective.

A producer shipping internationally therefore cannot treat lysozyme as one universal labeling question.

The destination market has to be checked before the treatment is used.

What Disclosure Reveals, and What It Cannot

The newer European ingredient rules reveal more than the old system did.

They still do not create a complete production record.

Bentonite used and removed is treated differently from tartaric acid incorporated into the finished wine.

Nitrogen used to protect a transfer can have a meaningful effect on aromatic preservation without appearing as an ordinary ingredient in the way a remaining additive would.

Lysozyme can create an allergen-disclosure obligation in one destination market and not the same mandatory obligation in another.

A wine fined with isinglass and a wine fined with pea protein can carry very similar ingredient information even though only one may satisfy a particular vegan certification or retailer standard.

None of this is inherently concealment.

It is the difference between a composition statement and a production record.

The two were never the same document.

The people who wanted a complete production record are not wrong to want one.

They are wrong if they assume the ingredient list gives them one.

The Bottom Line

Fining and stabilization are where the gap between what happens in the cellar and what appears on the label can become especially wide.

They are also where a winemaker's restraint is least visible to the person drinking the wine.

Every one of these tools has a legitimate use and a version of itself that can damage the wine.

Bentonite prevents haze and can strip aroma.

Charcoal can rescue a tainted lot and can empty it.

Gum Arabic can polish a good wine and can disguise a thin one.

Sorbate can prevent refermentation and, in the wrong microbial conditions, contribute to the geranium fault.

The material itself is rarely the whole issue.

The dose, the necessity, and the judgment are the real issue.

The best fining decision I make in many vintages is the one where the trial shows that the wine does not need anything at all.

I write down the result and walk away from the bench.

Continue the Wine Additives Series

About the Author

Sébastien Gavillet is COO of Wine Aromas - Le Nez du Vin. A renowned wine and whisky expert, winemaker, and distiller, Sébastien has been working with Le Nez du Vin for over 25 years. He is the author of Discovering and Mastering Single Malt Scotch Whisky and the International Whisky Guide series. He serves as a panel chair and examiner for The Council of Whiskey Masters, shaping global tasting standards and mentoring the next generation of spirits professionals.

Fining and Stabilization in Wine: What Gets Added, What Gets Removed, and What Must Be Disclosed