Matt Reid

Matt Reid

Winemakers get a lot of questions from the curious public. As a group, we are delighted when people take an interest in our craft, and happy to share our knowledge of the mystery, art, and science that is winemaking.

Some of the questions can throw us for a loop, but we do our best to answer. Once when I was discussing sugar measurement by refractometry to assess grape ripeness, one person in the group asked, “But cabernet grapes don’t have any sugar, do they?”

He looked deeply troubled and I imagine he struggled to reconcile his love of dry wine with the fact that the grapes might be sweet. But the alcohol has to come from somewhere.

Recently, many people have asked me if a certain wine is vegan. You might wonder how a product made from grapes and yeast might not be vegan. The answer has to do with the little understood practice of fining. Sometimes, a wine needs a little tweaking to meet its maker’s expectations. That’s where fining comes into play, and these techniques often involve animal products.


Fining is subtraction by addition. If a wine has something undesirable, or an excess of something desirable, the addition of a fining agent can remove or reduce that something. In most cases, the fining agent binds to what it is removing and precipitates out of the solution, leaving no trace of itself in the wine.

Fining in red wines

The principal reason to fine red wine is to remove excessive tannin. All red wines contain tannins, which come from the grape skins and seeds and, in some cases, from oak barrels as well. Tannins are compounds that, by definition, bind with proteins.

In your mouth, the wine tannins bind to your salivary proteins, which lubricate the mouth. They, therefore, have a drying or astringent effect. Too much tannin can make a wine rough, coarse or austere. The solution is to fine out the excess tannin.

Since tannins bind to protein, adding protein to a red wine will reduce the amount of tannin in that wine. The traditional protein used is albumin, from egg whites. Albumin in its pure form can be purchased, but most winemakers just add egg whites, since they are almost pure albumin. Other proteins that can be used include casein, derived from milk, and gelatin, which is derived from animal hooves, etc.

Vegetables do not contain as much protein as animal parts, but that has not stopped one company from bringing to market a fining agent derived from potato protein. Tannin reduction by fining can, therefore, be done in a vegan manner, but most winemakers continue to use albumin or other animal-derived proteins.

Fining in white wines

White wines are principally fined for the opposite reason as red wines — too much protein. Protein in white wines does not affect the flavor and is present in quantities too small to affect the wine’s nutritional value. However, if a white is exposed to excessive heat, during transportation, for example, the heat can denature the protein.

Instead of remaining invisibly in the wine, the protein is said to throw a haze, which can look like wavy bands or solid chunks. Whatever it looks like, the customer is going to recognize that something is wrong with the wine. White wines are fined to avoid this problem. However, the real problem remains unsolved. A fined white wine exposed to excessive heat will not throw a haze, but it will still be damaged if not ruined by the heat. The customer simply won’t know that this has happened.

Based on the red wine tannin-protein interactions described above, you might imagine that white wines are fined by adding tannin to remove the protein. Although that is done sometimes, it is actually trickier than it sounds. Any tannin left over after the protein precipitates out will add unexpected qualities to the wine that most winemakers would wish to avoid. Instead, a Kaolin clay known as Bentonite is added to the wine. The clay has numerous charged sites that attract the charged protein particles. The clay-bound protein then settles to the bottom, and the clean, protein-free wine is racked off the sediment.

All well and good, and all vegan. But there is another agent used to clarify white wines (and beer, too): isinglass. Isinglass is used to remove yeast (which are fungi, not animals), living or dead, from a wine to clarify it. Isinglass is a collagen-type protein derived from fish bladders, so a no-no for vegetarians and vegans. Very little of the material remains in the wine post-fining, so vegetarians who are more concerned with what they actually consume than with what was used in its production may be okay with isinglass, but no vegan would.


At present, producers are not required to indicate on the label what fining agents, if any, have been used in a wine. “Unfined” is frequently claimed on wine labels, but there is no legal meaning for the term. The TTB, the agency that regulates wines and their labels in the U.S., requires that statements on labels be true, but does not have much of an enforcement mechanism for this term.

For other items on the label, such as the origin of the grape or the grape variety, the validation and enforcement methods are more rigorous. Take such a claim with a grain of salt when you see it on a label.

Matt Reid is a UC-Davis trained winemaker working at Benessere Vineyards, consulting at Burgess Cellars, and co-owner of Calistoga-based People’s Wine Revolution.

Subscribe to Breaking News

* I understand and agree that registration on or use of this site constitutes agreement to its user agreement and privacy policy.

Matt Reid is a UC-Davis trained winemaker working at Benessere Vineyards, consulting at Burgess Cellars, and co-owner of Calistoga-based People's Wine Revolution.