"Send it back and ask for another bottle," Alexis Lichine advised restaurant-goers in 1951, "just as you would if you were served a bad egg." The cosmopolitan wine negociant and author—pictured on the dust jacket of his book Wines of France in a Bold Look gray suit, with slicked-back hair, Gauloises in hand—could do little more than offer centuries-old advice on this subject: sometimes good wine goes bad. That's why we endure the arcane tableside ceremony of presentation, cork-gawking and tentative tasting: not to sip and ponder whether we "like" it or not, as sometimes misunderstood, but to determine whether it's faulty.

There's the rub. As flummoxing as it is to find the "right" words for "good" wines, how many wine drinkers feel confident enough to call out a technically flawed wine—not to mention get a fix on which of the dozens of ailments of wine it suffers from?

Fortunately, few bottles are sent back these days, at least among the recently manufactured wines that are commonly consumed. In the 20th century, modern techniques made commercially produced wines more inherently stable. The wine hero of the 1950s wore a white lab coat and packed a Pyrex beaker in one hand, a refractometer in the other. In contrast, today's typical narrative celebrates Zen-like masters who are believed to get the best expression from their wine when they "get out of its way and let it do its thing," as the mantra goes. One might think that the white-coat set, having banished the microscopic enemies of wine, have moved on, victorious. That is not the case. They're here, and they're as busy as ever in the war against wine gone bad.

These days, much of the white-coat work is outsourced to professional laboratories like Windsor's Enartis Vinquiry. Providing a smorgasbord of extremely useful services to the industry, including alcohol testing for labeling requirements and analysis of grapes and wine for organic compounds and microbes, Enartis Vinquiry offers seminar series on wine blending, threshold testing and sensory of analysis of wine both good and bad.

This is the story of the bad.

The first rule about wine defects, sensory scientist Denise Gardner says—to a group that's largely been recruited by their employers to swirl and sniff the worst of the worst—is that everybody's different. Some might have a low tolerance for an aroma; others, a preference for it. Indeed, many of the worst offenders can actually add to a wine's aroma, when present in small amounts. Instead of debating in the manner of "I say tomato, you say tomahto," Enartis Vinquiry employs taste-preference panels and plots out the results in complex graphs. Some look like starbursts, others like city zoning maps.

Nobody can argue about plainly visual defects like "pinking," which occurs in white wine, or "browning" in red. Oxidation, the primary enemy of wine, can produce aromas of overripe apples, sherry or rancid nuts. Add volatile acetic acid or ethyl acetate, and get vinegar, rotting fruit or fingernail polish. The best cure here is prevention: simple, diligent cellar routines keep oxygen out of wine, and the addition of sulfites protects against oxidation.

Unless labeled "contains no detected sulfites," all wines have been treated with this preservative, in lower amounts than is typical for dried apricots. There's only one reason that wine could be rendered defective with sulfur: wine is made by people. If someone were to misplace a decimal when calculating a work order—just saying, for instance—an entire lot of high-end Napa Cabernet Sauvignon could receive a dose several factors above the legal limit. Luckily for them, there's an easy, if unappealing, cure: hydrogen peroxide neutralizes the sulfites. Before the Cab goes blond.

Hydrogen sulfide may sound similar, but there's a difference. Any naughty person who has thrown a rotten egg against a wall would recognize it. The grower could be to blame for dusting the vineyard with sulfur too late in the season, or the vintner for letting a fermentation bog down until the nutrient-deprived yeast literally pooped out. If it doesn't resolve, a light-blue dash of copper sulfate solution does the trick; eschew the heavy metal, and risk inviting the dreaded mercaptans.

These sulfide derivatives mimic a rank cornucopia of vegetable aromas—mostly cooked, some composted—from onion, cooked cabbage and asparagus to canned corn and natural gas. Again, there is a cure—but this time for only half of them.

Unlike the toasty, smoky aromas of fine oak barrels, "smoke taint" smells more like barbecue or campfire pit. Grapes soak up these aromas when the air is full of forest fire ash, as Northern California experienced in 2008. Worse than fire is the sun; when light shines too long on light-colored wine bottles—particularly sparkling—they may become "lightstruck," smelling of skunk, cheese or plastic.

Of no surprise to detractors of big, buttery Chardonnay, a surfeit of this characteristic is considered a flaw. The chemical responsible for the more aggressive aromas of malolactically fermented Chardonnay is diacetyl; little wonder that the "natural flavor added" to buttered popcorn is exactly that. Today, laboratories have engineered new lactic acid bacteria strains that reduce this tendency. Lactobacillus itself, when keeping the wrong company, may turn a buttery wine to a "mousey" one. It's not as cute as it sounds.

Brettanomyces is a particularly cagey bug, a type of yeast that shows up to ruin the party long after the good yeast has drunk its fill (actually, just the opposite) and gone. Brett is culpable for a yard-long list of aromas ranging from bacon, leather, clove and tar to wet dog, horse blanket, Band-Aid and creosote.

At minimal levels, some are desirable; isovaleric acid, the same that lends "vomit"-flavored Jelly Beans their novelty, is not. Brett is extremely persistent. On the other hand, the unique characteristics of some venerable chateaux are thought to be due to their resident brettanomyces.

Cork taint is the most insidious of all banes of wine, popping up in random bottles long after they've been shipped. "Corked" wine was the particular malady that Alexis Lichine warned us against 60 years ago. Contaminated cellars or moldy corks are the cause, but sanitary measures are not so simple: chlorine is a friend of 2, 4, 6-trichloroanisole. Whole cellars have been surrendered to TCA, which has a musty, wet-cardboard or dank-cellar aroma that flattens out or kills a wine's fruit. Improved cork manufacturing processes and screw-cap enclosures are viable solutions, while the consumer at home can take a shot at rescuing an affected bottle by pouring it over a sheet of plastic wrap.

If some of these bad actors sound really bad, there's little cause for worry. Methoxypyrazine is not an explosive chemical found in drug labs, after all; it's the "green" aroma typical to Cabernet Franc. A faulty wine is not likely to make anyone sick from drinking it, though, as the bugs that bring down the mightiest vintage are no match for the human stomach. Wines with minor, albeit recalcitrant defects are often quietly "disappeared" into a larger blend, and rarely must outright unredeemables be shown the drain.

Of more concern to the consumer is when a wine's technical flaws are passed off as representing its "terroir." Cynicism is seldom to blame; more often it's due to the inattention of wine bar staff or a vintner's self-deceiving "cellar palate."

There's a minor trend afoot to sensationalize the kind of additions that prevent or minimize wine spoilage as "manipulations." While it's true that among Enartis Vinquiry's self-admitted goals is to sell its analytical services and aroma-massaging additives, it's also entirely unlikely that the industry at large has any interest in jeopardizing millions of dollars of drinkable product for the sake of taking a philosophical position.

Just how much wine out there needs fixing? Enartis Vinquiry declined to divulge even a round number of such clients. (Perhaps the first rule of wine defects is that nobody talks about wine defects.) Seminar presenter John Katchmer, an enologist who spends his day in the ostensibly enviable task of tasting hundreds of wines, might lend us a clue when he says, "The joke is, you wouldn't want to drink the wine we drink all day."

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