Tartaric Acid (Wine Diamonds)

Tartaric Acid (Wine Diamonds)

I opened a bottle of wine and there were crystals around the bottom of the cork and the bottom of the bottle.  What is this?

This is crystalized tartaric acid, affectionately known by industry professionals as “wine diamonds,” or tartrates.   These crystalline deposits form in wines when potassium and tartaric acid, both naturally occurring products of grapes, bind together to form a crystal. Tartrates are scientifically known as potassium bitartrate, which is the same thing as cream of tartar used in cooking. They are completely harmless and natural. The formation of wine diamonds is less common in red wines, as their level of tartaric acid is lower, and crystals tend to fall out naturally during the longer barrel-aging process.

Why do wine diamonds form?

Tartrates are a normal byproduct of wine as it ages—but if the wine is exposed to temperatures below 40°F, wine diamonds can form within one week of a wine bottle’s exposure to extreme temperatures. It is these chilly conditions that make the tartaric acid compounds in a wine naturally combine with potassium to form a crystal. Why does tartaric acid remain in wine? All wine contains naturally occurring organic acids (malic and tartaric acids being the primary ones).

What methods are used to remove tartrates?

Winemakers employ a process called cold stabilization to remove tartrates from wine before it is bottled. Many producers do use this technique for purely aesthetic reasons with the hopes of eliminating wine diamonds

Do tartrates affect the quality of the wine?

No. The presence of tartrate crystals is viewed by many winemakers, sommeliers and academics as a sign of quality, indicating that the wine was not overprocessed. Wine crystals never impart an unpleasant taste.

How do you identify wine diamonds?

Potassium bitartrate can resemble crystalized sugar granules or crystal shards as they fuse together. They may appear as a powdery white substance at the bottom of a wine bottle. The crystals can also stick to the bottom of the cork.

How can tartrate crystals be avoided?

Delicate white wines that offer a suggestion of new oak, a hint of malolactic fermentation and a moderate approach to cold stabilization should be stored at 55 to 60°F and only chilled down to 45 to 48°F just prior to serving to mitigate the formation of crystals. When possible, wines should not be stored in refrigerators overnight that maintain temperatures lower than 45°F.

How should I serve wine that has tartrate crystals?

If wine diamonds appear on a cork, simply wipe them away with a cloth. If their appearance in a glass is disagreeable to the consumer, decant the last quarter-bottle of wine, leaving any crystals behind. Pouring through a cheesecloth is also acceptable.

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