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Almost all of this stuff has been removed by the time the wine reaches the bottle, so what you end up drinking is grapes and little else. But some chemical secrets of winemakers will be unveiled by the new Food Allergen Labeling and Consumer Protection Act signed into law in August 2004, by President Bush.

Milk, eggs, and fish are potential allergens, and each is used in winemaking. All three are part of a class of substances called fining agents, and in theory all are completely removed from the wine before bottling. Fining agents are just one class of chemicals used during the winemaking process to give grape juice a makeover. Some winemakers also use flavor enhancers and correctors, coloring agents, and yeast nutrients.

Perhaps the most famous wine additives are sulfites which concern people enough to already merit their own warning label. Sulfites are crucial for preventing wine from spoiling and have been used in some form for centuries. Recent research appears to acquit sulfites of culpability for “Red Wine Headache Syndrome,” but some asthmatics may react to their presence.

It would be nice if vegans, asthmatics, or anyone sensitive to a particular additive could scan the bottle’s label to see a list of everything that has gone into making the wine. But until labeling laws change drastically, sensitive wine drinkers will have to settle for calling the winery for information about additives. Most people have no reason to think about what might have been in the wine they’re drinking, and never would think about it except when they’re prompted to ask, “Hey, what are those things floating in my glass?”

Fining Agents
Fining agents remove elements that could affect the appearance or texture of the wine. For example, winemakers seeking to soften the texture of a highly tannic red wine might add egg whites or gelatin. Fining agents are added to a tank or barrel of wine. The substance grabs onto whatever solid matter it has an affinity for, and over a number of days carries it to the bottom. The wine is then drained off leaving the residue and the fining agent behind.

Different fining agents are used for different purposes. Isinglass, an extremely pure gelatin produced from the bladders of sturgeon, is used mostly in white and sparkling wines to improve visual clarity and purify aroma. Bentonite, a volcanic clay, removes proteins for better clarity as well as stability during long-term storage. Egg whites are used almost routinely in red Bordeaux and are also used to remove bitterness from Sherry in Jerez, Spain. Once it was common throughout that district to see Sherry houses separating eggs to use the whipped whites for fining the wine. What became of the yolks? Restaurants all over the district would routinely offer dishes with béarnaise and hollandaise sauces!

One fining agent popular with red-wine makers is a substance similar to ground-up nylon called polyvinyl polypyrrolidone, PVPP for short. A patented product of GAF Corp., PVPP is used to remove the pink color from some white wines. Because it can remove very small molecules, it also helps reduce bitterness. Small tannins are bitter; larger tannins are less so. Removing the smaller ones is helpful to keeping a red wine from being bitter.  

A new technology accomplishes the same task in a different way. Vinovation, a Sonoma County technical consulting firm, uses a patented French process called micro-oxygenation that helps small tannin molecules clump together. [Fewer, larger arrays of tannin have much less contact with the mouth than dispersed molecules because they have less surface area. The resulting wine is perceived as less tannic.]

Flavor Correctors
The most common addition to wine is acid. Almost all wines in California have their acid “adjusted,” which is winespeak for an addition of acid to accommodate for a deficiency. Insufficient acidity makes a wine taste flabby or flat. Acid additions do not change the aroma of a wine, but can increase tartness. Most acids supplements are natural, such as tartaric or citric.

Tartaric acid, in fact, is the strongest and most common naturally occurring acid in wine grapes. It’s responsible for glass-like crystals, or tartrates, that form in some chilled bottles, often just under the cork. While completely harmless, the crystals taste as tart as the acid they come from. They’re often removed in the winemaking process, mostly for visual effect, and some wineries collect and sell them to companies that make cream of tartar which is used to help cake rise.

A few winemakers also use trace amounts of ascorbic acid (vitamin C) in some early-drinking white wines. It acts as an oxygen scavenger and keeps the wine fresher. What if a wine is already too tart? Some winemakers add potassium bitartrate which does the trick.

Consumers love the flavors of vanilla and wood that come from oak barrels. But new oak barrels are expensive, so makers of inexpensive wines sometimes take a shortcut, adding oak chips or even powder to a wine being made in a cheaper container. The oak is removed before bottling, but that oaky flavor remains.

Flawed wines can sometimes be “rescued.” Wines that have developed hydrogen sulfide (H2S), and thus are termed “reduced,” can have a rotten egg smell. Copper sulfate is a common solution to deal with H2S. The copper reacts with the H2S to eliminate the stink. Copper has its drawbacks because it is also an oxidation catalyst and can shorten the life of a red wine.

But copper can be the consumer’s friend. When you get a wine that has a slight hint of that rotten egg smell, drop a penny into the glass and after a minute or two the H2S smell should drop or be wiped out. Old pennies have more copper than newer ones and work better.

Coloring Agents
For years, dark Petite Sirah and Alicante Bouschet were routinely added to pale-colored red wines. They, however, add flavors of their own, and even as little as 2 percent can sometimes dominate the taste of a more delicate varietal.

Over the last decade, a number of companies have developed stable color additives, including one introduced in 2001 by Canandaigua Concentrate, a division of the wine company of the same name. Called MegaNatural, the substance is derived from grape skins and, according to the company, “can be custom-formulated into a wide range of shades of red, including Pink Grapefruit, Strawberry, Cranberry Red, Cherry, Raspberry, and the variations in-between.”

Yeast Nutrients
Yeast is essential in the winemaking process, for it converts the sugar in the grapes to alcohol. If the yeast dies off before fermentation is complete, the remaining sugar will make the wine sweet, like a dessert wine. Yeast nutrients -- the most common is diamonium phosphate, a nitrogen source -- contain vitamins and amino acids that keep yeasts healthy so a wine can completely ferment to dryness.