I recently opened a bottle of red wine and saw this on my cork:
Wait, what was THAT?? Was it broken glass, sediment, or sugar? Had my wine gone bad?
Well I was happy to find out that those are tartrate crystals, or better known as wine diamonds. These crystals are a harmless byproduct of wine and have no aroma or flavor and don’t affect the quality of the wine.
How are they formed?
These crystals are formed when tartaric acid (a natural component found in grapes) binds with potassium in cold conditions. The compound that is formed is called potassium bitartrate. It’s the same thing as cream of tartar used in cooking.
Tartrate crystals can be found in red and white wines, but white wine tends to contains more potassium bitartrate. Since white wines are served chilled, the crystals will form. So what wineries will do is help remove these crystals by cooling their white wines to near freezing temperature before bottling so that when a consumer does chill a bottle, the crystals won’t be there.
What if my wine has wine diamonds?
There is nothing to fear if you see these in your wine. What it means is that the wine was not cold treated when being made. And some wine experts will tell you that these wine diamonds are a sign of a higher quality wine because the wine making process happened without much inference or filtering, thus keeping the original flavors and aromas intact. Remember they have no taste, so you can filter them or just have a little crunch if you drink them.
So I guess you could say diamonds are a wine lover’s best friend!