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(Credit: Vera Chinese)

As the aged Italian winemaker lay dying, he called his sons to hear his last words. Leaning over their father, Angelo and Carlo barely heard him whisper, “You can also make wine from grapes.”

Substitute French, Spanish, Portuguese, Californian or vintners from any other region to the joke and it still works. Yes, the basic ingredient in wine has always been grapes, but since the dawn of time winemakers have added other materials in order to “fine” or improve the quality of their fermented grape juice. From beakers of seawater to blood to the charred remains of the rodent that fell in the vat, over the centuries judicious use of “adjuncts” has allowed vintners to rescue damaged grapes, ameliorate fermentation flaws or stabilize perfectly made wine.

Here in the United States, winemakers are limited to a federally approved list of additives for both fermentation and finishing of wine. With harvest currently underway on Long Island, our own winemakers have already made many decisions about whether or not to take advantage of this arsenal because most of it needs to be ordered before harvest. FedExing heavy packages overnight from the California suppliers if a problem arises could more than double the cost.

Meanwhile, for the consumer outside the winosphere, there is an increasingly loud buzz in favor of “natural” winemaking (a term not defined by law). Several respected wine opinionators have published various iterations of the additive list, usually without explanation. Since they apparently don’t know how or why these are used under real conditions, I thought it would be useful to explain the most common ones so you can decide for yourself whether to expect you’ll break into a rash for lack of ingredient labeling.

Sugar: If grapes don’t have enough natural sugar to convert to at least 10 percent alcohol, crystallized sugar may be added to compensate. Legal in France (and here), “chaptallization” helps a winemaker pick for freshness rather than for alcohol. In warmer regions, over-ripeness is more of an issue and water may be added to compensate for excess sugar.

Potassium metabisulfite: Augmenting naturally occurring SO2 in wine, it is most active in low-pH, high-acid wine (which needs it least) and is usually added at the rate of 15 to 50 parts per million, often at crush, transfer to barrel, topping and bottling. It is the most effective antioxidant and antibacterial agent available, used for centuries. You may be allergic to SO2 but if you can safely eat a Fig Newton or a golden raisin (which have far more SO2 than wine), you’re not. Imported, bulk or sweet white wines generally have the highest levels, which may give you a headache.

Pectic enzymes. Naturally occurring in grapes but added in tiny amounts to increase the flow of juice from pulpy skins, these enzymes also help clarify the must.

Tartaric acid: The predominant acid of grapes, it may be added as potassium bitartrate to lower the pH and hence stabilize or freshen juice or wine.

Bentonite: An insoluble clay made of ionized fossils, used to clarify juice and remove protein that would cloud the wine.

Tannin. Naturally occurring in grapes, this is added to help bitter molecules form longer chains so they become smoother and more stable.

Cultured yeast and yeast foods like nitrogen (from diammonium phosphate or DAP), thiamine, B6 and vitamin C (ascorbic acid) are used to ensure complete fermentations. Some vintners rely on indigenous yeast but most will add cultured yeast if faced with a stuck fermentation.

Oak chips, beads or barrels: Used to add complexity, balance perception of alcohol, clarify and purify wine.

Natural fining agents used to eliminate off odors, flavors or colors include egg white (albumin), isinglass (sturgeon bladder protein), milk and gelatin. Most of these are proteins that precipitate out of solution. Carbon (charcoal) is used to decolorize or deodorize (remember that charred rodent?) and PVPP is a sort of plasticky additive that strips out nasty aromas.

This is an incomplete list (in the interest of space), but you can see that most of these adjuncts are either gobbled up during fermentation, precipitate out before bottling or augment naturally occurring stuff. If ingredient labeling were required, would things that were added but are no longer in the wine count? What about additives not on the list, used surreptitiously, like raspberry extract? What about processes like reverse osmosis, spinning cone, nanofiltration?

In winemaking, conditions are not always perfect and interventions are needed. Bottom line: Do you like the wine?

Ms. Hargrave was a founder of the Long Island wine industry in 1973. She is currently a freelance writer and consultant.