How to Tell If Your Wine Has Gone Bad

Faults and flaws exist in all aspects of life, and the world of wine is no exception. From cork taint to oxidation and beyond, a number of flaws can arise during the winemaking process, and some of these faults can make it into your bottle. 

However, some of these imperfections aren’t as terrible as they may seem. We asked three industry experts to break down the most common flaws in wine, as well as how to spot them, experience them, and perhaps even enjoy them. 

Cork taint, Brettanomyces, and volatile acidity

According to Dr. Jamie Goode, wine journalist and author of the book Flawless: Understanding Faults in Wine, the most obvious wine fault is cork taint.

“[Cork taint] occurs when fungal metabolites [often referred to as TCA, an abbreviation for 2,4,6-trichloroanisole] from the cork end up in the wine,” he says. This results in aromas that typically come across as musty, damp cardboard.

However easy it is to blame cork taint for off aromas and flavors in wine, not every issue is the result of TCA contamination. Goode highlights the equally common fault of Brettanomyces, which is often simply referred to as Brett. 

“[Brett] is caused by a rogue yeast of the same name that finishes off the fermentation or grows after fermentation has finished, and creates savory, slightly medicinal flavors in the wine that can range from band aid to animal sheds and farmyard smells,” says Goode. 

Edouard Bourgeois, wine director at Pressoir, a New York-based wine experience company focused on tastings and events, adds that it only takes a small concentration of Brett to contaminate a whole vat of wine — or even a entire winery — which is why winemakers generally need to act quickly if they detect its pesky presence. 

Not every flaw is the result of yeast or bacterial contamination, though. More nuanced chemical reactions are sometimes the culprit.

“Another possible flaw in wine is volatile acidity, otherwise known as VA,” says Bourgeois. He describes the condition as a concentration of acetic acid in wine, noting that excessive amounts of volatile acidity can cause a wine to dance a fine line between tasting like wine and vinegar. 

Wines afflicted by volatile acidity may taste sharper, slightly sour, or feel prickly, or lightly carbonated on the tongue. However, some winemakers, particularly those in the natural wine space, have chosen to embrace a touch of VA in their wines, as small amounts can sometimes add interesting twists to the aromatic spectrum of a bottle. 

Oxidation vs. reduction

Two of the most highly debated faults in wine are oxidation and reduction. Goode explains that in chemical reactions, oxidation and reduction are opposites, but in wine, they aren’t. 

“Oxidation is when oxygen adversely affects the flavor of wine,” he says. “Fruity characters are lost, the color fades, and the wine tastes savory, often with notes of apple and hay and even earth.” 

Reduction refers to the presence of odorous volatile sulfur compounds in wine. “These range from the simplest, hydrogen sulfide, which smells of eggs and drains, to more complex ones, which have a range of different smells,” says Goode. He notes that some volatile sulfur compounds can actually be positive in small doses. 

Some winemakers may choose to refrain from oxygen exposure and keep wines in a reductive environment to protect them from oxidation. 

“While oxygen can be useful to open up and develop aromas in wine — it’s the reason why you swirl the wine in your glass or decant it to let it breathe — it can also become wine’s enemy [in larger doses],” says Bourgeois. Overexposure to oxygen can disfigure the aromatic profile of a wine, as well as affect its ability to age properly, reducing its lifespan. 

Are wines with faults still enjoyable?

Christina Rasumussen, the co-founder of Little Wine, a U.K.-based platform focused on managing information and data, explains that some wine faults are more distinguishable than others, and all faults can appear on various sides of the spectrum, from barely noticeable to severe. 

“People have different abilities to pick up certain tastes and smells, and this isn't just limited to wine faults; it's also the case for certain flavors such as pepper, which the compound rotundone is responsible for,” she says As a result, one person may not sense what another person is picking up. 

This begs the question, is a perceived fault actually really a fault, and whose palate should we use as a measure?

While some people may find the matchstick notes found in reductive wines to be unpleasant, many wine lovers enjoy the added layer of complexity it can bring to a wine. This argument can be made for most faults, save for cork taint, which all experts agree is largely intolerable. 

Goode says that small traces of flaws can be quite interesting in wines. “For example, the vinegary smell of volatile acidity isn't nice when it is obvious, but at low levels, it adds complexity,” he explains. 

Bourgeois agrees, elaborating that there are many different levels of tolerance for faults. “A bottle can be obviously oxidized and then there is no question,” he says. “On the other hand, a wine can be slightly affected by volatile acidity which, in small proportion, may in fact provide an interesting aromatic element in the wine.” 

Rasmussen says that she and many other drinkers enjoy volatile acidity in wine at lower doses, particularly in warmer vintages, as it can add an element of freshness to a wine. 

“In high doses, however, it can be highly unpleasant, giving the wine notes of vinegar or nail polish remover,” she says. 

While there is no health risk to drinking a corked or oxidized wine, the excessive presence of faults can cause the balance of the wine to be off, rendering the experience of drinking it rather unenjoyable. 

“People differ in their sensitivity to different smells, so they don't all experience wine faults the same,” says Goode. “This adds another level of complexity.”