Tag Archives: potassium bitartrate

What Are Those Shiny Crytals on the Cork?


Question from Steve: I opened a bottle of white wine and it had these shiny crystals, kind of like sugar on the cork. Is that wine okay?

Reply: Hi, Steve. Thanks for writing! Yup, it should be just fine.

A great thing about wine is that even if it’s spoiled it’s not harmful – unless you drink too much, of course! The worst thing that happens is you’re offended by the smell or taste, in which case you should take it back or dump it.

MAJOR DIGRESSION: Please don’t use bad wine for cooking. That weird flavor is what you’re adding to the dish, just like any other ingredient, and cooking it down will just concentrate the weird flavor.

So, what’s with the crystals? It’s really quite common to come across them, especially in white wine. They’re not sugar – they’re mainly composed of tartaric acid, which is a very strong acid, and the main acid found in white wine. As you see, they can also be suspended in the wine.  Continue reading

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What’s that Shiny Stuff on the Cork?

Question from Sarah: When I opened a bottle of white wine there was shiny stuff on the cork. Is that sugar or what? Does it mean there’s something wrong with the wine? Thanks for your help.

Reply: Hi, Sarah. Thanks for writing! Those crystals aren’t anything to worry about. White wine tends to be high in acid, especially tartaric acid. The crystals, which are usually called “tartrates”, sometimes form during production and also when the wine is cold for a period of time – for instance when you store it in your fridge. The tartaric acid binds with potassium to become potassium bitatrate or cream of tartar! Wineries can remove tartrates through a process call cold stabilization, but it doesn’t much matter one way or the other. When you visit a winery, sometimes you can see the tartrates shining inside an empty barrel. Next time it happens, you can look very knowledgeable by telling your friends “Oh, don’t worry about that – it’s just tartrates.”

Trivia: Lots of people like to call the tartrates “wine diamonds”!

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