What’s The Gunk in My Wine? | Wine Enthusiast
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What’s The Gunk in My Wine?

When you tilt a cup of espresso for that last sip, it shouldn’t come as a surprise to spy some tiny sugar crystals stuck to the bottom. It’s not cause for concern and simply means you didn’t stir long enough to dissolve the sugar you added.

But a minor alarm often goes off when a similar scenario unfolds in a glass of wine. When tiny white or red crystals, or a dark, reddish sludge appears from an almost-empty glass, it’s time to rinse and refill.

Red liquid being hosed through a metal mesh screen

What is wine sediment and is it dangerous?

Is sediment in red wine really a cause for concern? Are crystals in white wine dangerous? Is it safe to drink wine with dregs of various sorts in the bottom?

The answers to these questions? No, no, and yes. Kind of.

Almost always, when sediment, dregs or the little crystals also known as “wine diamonds” appear in the bottom of a glass, they present no danger. It’s often a sign that the wine was made with minimal intervention.

When sediment, dregs or the little crystals also known as “wine diamonds” appear in the bottom of a glass, they present no danger.

Most of the time, sediment in wine is either tartrate crystals (“wine diamonds”) or spent yeast, called lees, which are both natural byproducts. Neither is harmful to your body.

But if you don’t see the sediment before it’s on your tongue, you might gag on this gunky little surprise.

To get rid of sediment quickly, pour wine into a decanter or any good-sized pitcher, through a fine-meshed sieve, a few layers of cheesecloth or a paper coffee filter. It’s smart to rinse the coffee filter first with hot water.

Red wine gushing through filter

Natural tartrate crystals

Tartrate crystals are bits of potassium bitartrate or calcium bitartrate that have fallen out of solution in the wine. They’re more common in white wine and usually happen when wine has been refrigerated for a long time. If you remember from chemistry class, heat can help solid substances dissolve in fluids, while cold can force them back into crystal form.

Potassium and tartaric acid are two natural components of grape juice. They link up and remain in wine after fermentation, when yeast turns the grape sugars into alcohol and carbon dioxide. Most of the world’s commercial wineries prevent this through cold stabilization, a process that causes the tartrate crystals to precipitate out of the solution before being bottled.

One technique involves chilling the wine below 32°F for up to three weeks via temperature-controlled tanks or cold rooms. Afterwards, the potassium bitartrate crystals left in the tank can be gathered, finely ground and sold as “cream of tartar.”

Labs and companies have devised other methods of tartrate stabilization. One employs mannoproteins extracted from the cell walls of yeast. This came from the observation that wines aged on the lees, which are the sediment of mostly dead yeast cells left after fermentation, are less likely to develop tartrate crystals after bottling. Another method, electrodialysis, passes the wine against an electrically charged membrane in a sophisticated filtration unit.

Red wine means lees sediment

Many wineries stabilize their white and rosé wines, but not their reds. There are two reasons for this.

Most high-quality red wines are aged on their lees for at least a few weeks. Thus, they’re less likely to shed their tartrates later. White wines, though, are aged on their lees less often.

Second, most popular red wines don’t need to be chilled to taste their best. This means they’re less likely to be refrigerated and form tartrate crystals in the bottle.

But the other form of sediment, lees or dregs, is almost always a red-wine phenomenon. More specifically, it’s a phenomenon in well-aged red wines.

Types of Wine Sediment
White wine: Tartrate crystals, or “wine diamonds”
Red Wine: Lees, or spent yeast

Winemakers use whole crushed grapes—the skin, juice, seeds and pulp—to make red wine. Only the juice and pulp are used to make white wines. Red wine gets most all of its color and much of its aroma, flavor and texture from the skins. Because of this, red wine has more grape particles suspended or dissolved in it.

A new wine is full of skins, seeds and bits of stems, as well as used-up yeast cells from the fermentation process. A portion of these stay in the wine.

A lot of that debris falls out while the wine ferments and ages. Then, when the winemaker pumps, or “racks,” the wine, those lees stay behind and are removed. But microscopic solids remain, even after the wine is pressed, aged for months and filtered.

After many months or years in bottle, some of that stuff will form a fine silt or sediment of lees at the bottom. This happens in almost every good, ageworthy and tannic red wine, whether Bordeaux, Barolo, Rioja or California Cabernet Sauvignon. The fine sediment can form a visible lengthwise strip if a bottle lays on its side undisturbed for years or decades.

Top view of decanter and wineglass with red wine on the wooden table

Can you decant?

The lees won’t hurt anyone, but few people really want to drink them. Luckily, decanting was invented for just this purpose.

The idea is to pour the wine off the lees slowly, so they stay in the bottle. A flashlight can help with this. If you place a light under the bottle as you decant, you can see when the sediment starts to move into the neck. That’s when you stop pouring.

Before you decant, it’s critical to get all of the lees collected onto the bottom of the bottle. If the wine has rested on its side, stand the bottle upright for a few days before decanting.

But remember, this is not rocket science or a master sommelier exam. If there’s no time to wait, or if you fumble the decanting, just pour the wine into your guests’ glasses. When they get to the bottom and wonder how sediment got into their wine, you’ll know what to tell them.