Monday, May 09, 2005

Email: Preservative & stabilizers

Bill writes in an email…
Most wines are pumped full of stabilizers and preservatives. They're drinkable but have no character. Why not admit this and put an end to all the hokum used to describe them ?

Hmmm...this is really two issues: preservatives (which are usually present in the final wine) and stabilizers (usually applied to the wine and then are removed). So for the preservatives let's see...there's Sorbate, Sulfur, and Ascorbic acid (Vitamin C).
Vitamin C is useful against oxidation of the wines, but is usually used in conjunction with a small amount of sulfur dioxide, as it doesn’t directly inhibit growth of yeasts and bacteria. Some vintners utilize it to produce wines with less SO2 in the final blend.
Sorbate isn’t used very often for two main reasons: first it needs to be in concentrations which usually cause some sensory effects (off aromas), and second, it can be metabolized by lactic acid bacteria (LAB) into some substances like geraniol (oil of geraniums), which isn’t good for the nose of the wine either.
Sulfur (sulphur) is the most common preservative used in winemaking, and has been in use in one form or the other since the dark ages. It’s very broad spectrum in its effects, working at lower levels as an anti-bacterial agent, and anti-yeast agent at higher levels. People who are prone to asthmatic reactions may experience problems at higher concentrations (say above 40 to 50 ppm free SO2), but again, concentrations at those levels and greater usually cause some sensory problems for the wine, and most vintners avoid excessive use.

That's what MOST wines would have as preservatives, and all those substances are FDA coded as GRAS (Generally Regarded As Safe).
DMDC (almost exclusively used as a wine-in-box preservative) might also be seen from time to time, though it's expensive and requires special handling and dosage equipment.

All these substances are usually applied at levels less than 100 ppm which leaves the wine 99.99+% pure wine minus any water percentage they used during the process, which again is minimal (unless you want to discuss the very small minority of truly unscrupulous vintners) and controlled by federal law. (I believe the legal max concentration of DMDC is ~200 ppm.)

Filtering, fining and stabilizing aids are added to a wine where they react with whatever substance in the wine you’d like to remove, then fall out or are filtered away from the wine. For example, egg whites can be used to remove too much tannin from a wine (tannins react with the albumen [protein] which then precipitates, and the wine is racked off of the solids). Other proteins (casein [milk] and isinglass [swim bladders from sturgeon] being the most common) may be used depending on what country you’re in. Some producers in France’s Rhone had used bull’s blood (another source of protein) for centuries as a traditional way too remove excess tannin from their wines.
Other processes may use bentonite or kaolin clays to remove proteins, or household cream of tartar to keep excess acid from forming crystals in the bottle when chilled. Almost all of these are GRAS substances as well.

There are some more uncommon additives, but only really low quality vintners would be using those in any sort of ‘regular’ basis. Otherwise you just wouldn’t see those used in mainstream wine production (at least not in the USA).

And my experience is that wineries who have used stabilizers do so sparingly, and infrequently (those additives aren't cheap to buy & put in there). Stabilizers are (generally) used when the fruit sourced for the wine is falling apart and doesn't clarify easily (translation: really inexpensive wine) there's a strong economic incentive to NOT place those substances in the wine (e.g., higher overhead and less return on your investment $).

The complete list of those substances which can be used for the Storage, Treatment and Finishing of Wine can be found here:
[the list differs in other areas (e.g., the EU) but I'll address that more in the future]

Happy reading!


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