What are tartrates?

Tartrates, affectionately known by industry professionals as “wine diamonds,” are tiny, crystalline deposits that occur 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 by-product of wine as it ages—but if the wine is exposed to temperatures below 5°C, wine diamonds can form within one week of a wine bottle’s exposure to extreme,. 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). Malic acid— “malum” is Latin for “apple”—can almost entirely be converted to the weaker acid, lactic, through a bacterial fermentation. Tartaric is the primary acid we taste in all wines; it is essential to a wine’s mouth feel and balance. Tartaric acid tends to be more stable in wine, unless the wine is exposed to very cold temperature. Ensuring the perfect balance of these acids in a wine while minimizing the chance for wine diamonds to form is truly where art and science converge.

What methods are used to remove tartrates

Winemakers do employ a process called cold stabilization to remove tartrates from white and rose wine before it is bottled. Many producers do use this technique for purely aesthetic reasons with the hopes of eliminating wine diamonds. The old standard for cold stability in  winemaking was 0°C for 10 days, which is only acceptable if you are selling a product that is mass marketed at a very low price. Very cold stabilization strips a wine of its aromas and flavours, so at Best of Spain we  cold stabilize our Verdejo and Rose  in a natural way, allowing the wines to  get cold during winter (a cold, winter day of the Northern Spanish Plateau  is around 4 degrees), depending on the delicacy of the vintage we will leave the wine more time or less. Maintaining our quality and consistency is critical to our reputation, so we don’t resort to extreme measures of cold stability that put quality of taste at risk. Also it is chemical additives that added to the wine avoid this crystals, but of course this is not in our philosophy of making wine.

Do tartrates affect the quality of the wine? No. Actually, the presence of tartrate crystals is viewed by many winemakers, sommeliers and academics as a sign of quality, indicating that the wine was not over processed. Wine crystals never impart an unpleasant taste.

How do you identify wine diamonds? Potassium bitartrate can resemble crystallized sugar granules or crystal shards as they fuse together. They may appear as a powdery white substance at the bottom of a wine bottle.

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 15 to 20°C and only chilled down to 8 to 10 °C 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 10°C.

 How should I serve wine that has tartrate crystals? In a glass is disagreeable to the consumer, decant the last quarter-bottle of wine, leaving any crystals behind. Pouring through a cheesecloth its also a good solution. Or just avoid pouring the last 5 mls of the bottle, a little price to pay for drinking healthy wine.


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