The Cellar Dweller
A typical bench test for protein stability in white wine. There is a haze with the highest level of treatment. A stable bentonite
suspension was created.
GARY STRACHAN Wine so fine — or not
A close look at the various fining agents, and why it’s vital not to over-use them. By Gary Strachan
I
have a love-hate relationship with wine fining agents. In a perfect world all the sediments that occur in wine would settle out nicely and you could simply remove the clear wine via the racking valve. In the real world it’s seldom that simple, except in some red wines. The relatively new technology of cross-flow filtration can potentially overcome the need for fining agents, but the high cost of buying one of these units puts them out of reach for many small wineries.
By definition, a fining agent for wine is a processing aid used to remove unwanted substances by adsorption to an insoluble fining agent. The fining agent is not an ingredient. Many fining agents exhibit their activity because of their surface charge at wine pH. Proteinaceous fining agents such as gelatin or isinglass have a positive charge. Tannin and bentonite have a negative charge. In practical use, adding gelatin to a wine will remove
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tannin, or adding bentonite to a wine will remove protein.
Red wines typically have enough natural tannin content that bentonite is not required to remove protein. It drops out with some of the tannin and is discarded in the lees. In white wines, there is often enough soluble protein to cause an eventual haze or precipitate, referred to as heat instability.
To test for heat stability, a wine in
process is either heated or acidified to determine if it will become hazy. If the wine fails the test, a series of bentonite levels are tested on the bench to determine the effective treatment to create stability. It is important to not over-fine a wine. Flavour can be removed by bentonite, or a high level can cause a colloidal bentonite haze, which can only be removed with a
proteinaceous fining agent. A similar Producers of Quality
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