Why are there crystals in my wine? – ask Decanter

Don't panic, you're probably not about to die from eating broken glass; those little shards in your wine are more likely to be tartrate crystals. Gerard Basset OBE MW MS explains how they got there...

 Tartrate crystals on a cork pulled from a bottle of red wine. Credit: John T Fowler / Alamy
Tartrate crystals on a cork pulled from a bottle of red wine. Credit: John T Fowler / Alamy

Tartrate crystals in wine

Howard, via email, asks: I recently opened a bottle of a favourite Jurançon Sec that I’ve had in the cellar for five years, to find a lot of tartrate crystals floating about in it. Once these have occurred in a wine, will they ever disappear again?

Gerard Basset OBE MW MS replies:

Many people think these clear crystals floating in the wine or stuck to the cork are salt, sugar, sediment or even broken glass.

In fact they are harmless by-products of wine, and some equate their presence as a mark of quality, in that the wine has not been overly manipulated in the cellar.

When exposed to cold temperatures, the tartaric acid naturally found in grapes binds with potassium to form a compound called potassium bitartrate. It’s the same as cream of tartar used in cooking.

Many white wines often undergo a cold stabilisation process to remove these tartrates before bottling, but often some are left, ready to crystallise in your cold cellar or fridge.

Once formed they’ll never disappear, but they won’t affect the aroma, taste or quality of the wine.

If you find them unsightly, you can either decant the wine before serving or filter it through a muslin cloth.

Translated by Leo / 孔祥鑫

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