Wine ClarificationNovember 21, 2011

By John St. Mark
Egg Whites, Clay, Fish Guts… What Are They Putting In My Wine?

In recent years there has been some controversy surrounding the use of certain materials and processes in winemaking, and the argument has been made that agents used to process wine should be covered by labeling regulations. Why do they use that stuff?

Immediately after grape juice has fermented it contains particulate matter in suspension and unstable compounds that could, over time, affect the wine adversely (for example, micronutrients could support the growth of bacteria that would spoil the wine.) Traditional methods of clarification (removal of unwanted substances) include the following:


If the wine is allowed to rest in a stationary container (such as a barrel) heavier substances will eventually settle at the bottom. "Racking" refers to draining or siphoning the wine from one container to another, leaving sediment behind in the first vessel. This is the simplest and gentlest method.



New wine may contain unstable compounds that are not heavy enough to be removed by racking alone. These can eventually bond with other substances in the wine, creating cloudiness or haze. Unstable, astringent components (specifically, excess tannins) can bond with the proteins in saliva, creating that dry, gritty sensation in the mouth associated with tannic wine. "Fining" occurs when an agent is introduced that will bond electrochemically with undesired compounds (flocculation) rendering them heavy enough to be racked out (the racking process will eliminate the fining agent as well.)

A number of different fining agents have been used historically, and various agents are still used depending on what the winemaker wishes to eliminate; in modern winemaking one may find egg whites, casein, isinglass and bentonite used frequently. Fining is not always necessary, but under some circumstances it can significantly improve the wine.

Although it has been argued that fining agents should be specified on wine labels, many people in the industry believe that this would only create confusion because the fining agents are no longer present in the finished wine. I know of no instances of consumers being adversely affected by fining agents, due to allergy or any other reason, however it is not possible to demonstrate conclusively that the wine will never contain any trace of these agents, and some consumers may object to the use of animal products in food production as a matter of general principle (the egg whites are from chicken eggs, casein is derived from milk products and isinglass is made from the swim bladders of fish. Bentonite is a kind of clay, which is usually mined.)

It should be emphasized that this is not new technology; fining is a very old, traditional practice used throughout the winemaking world.


A number of different types and grades of filters are used in winemaking, depending on the specific goal (that is, depending on what the winemaker wishes to eliminate.) Like fining, filtration is not always necessary, and excessive filtration can strip away substances that contribute to the wine’s quality, so the process is sometimes criticized; many winemakers believe, however, that the appropriate use of filtration will not detract from the wine and can sometimes significantly benefit the finished product.

Generally, the less you have to do to the wine, the more it will reflect the unique characteristics of the vineyard and the vintage. Producers espouse different philosophies regarding how winemaking tools should be used but what is truly important is that they use the resources at their disposal to make the best possible wine, and that, of course, is a matter of taste.

You can read more of John’s articles, which include; Wine Tasting Basics, Wine Aromas and Flavors, Wine & Cheese, Wine Tasting In The Napa Valley, and more in his column on

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