"Always carry a corkscrew and the wine shall provide itself."
Tartaric Crystals in Wine: the "Wine Diamonds" of Quality
Have you ever come across what appear to be white flakes in your bottle of wine? Did you immediately assume that these crystals somehow meant the wine was flawed or ruined? What you had most likely seen are tartaric crystals, commonly referred to as wine diamonds or Weinstein (wine stone) in German speaking countries.
Tartaric acid is a normal grape acid. Potassium also exists in grapes, and when these two things bind together under chilly conditions, they form small potassium bitartrate crystals, which then settle to the bottom of the bottle.
There is an interesting correlation between wine stones and the quality of a wine: the longer the grapes hang on the vine, the more acid will accumulate in the grape. Furthermore, the more time the wine is given to ferment, the less wine diamonds will fall out during fermentation, but the more they will instead build up later in the bottle.
In other words, wine diamonds are an indicator that the grapes ripened for a long time and that the Winemaker fermented the wine slowly and with great care. Both are important precursors to crafting high quality wines.
Are Tartrate Crystals harmful?
No, tartrate crystals will not harm you if you happen to swallow a few. For the most part they might be esthetically unpleasing.
In fact, crushed tartrate crystals are the same thing as cream of tartar...yes, the same stuff you have in your pantry right now. Wine barrels used to be a major industrial source of tartrate crystals for the production of cream of tartar.
... and what to do with it? I found myself in the unique position of having a bunch of open red wine bottles after a dinner party. What could I do with the wine besides drink it? First and foremost, I learned that you can actually freeze wine to be used later (it won’t be good to drink, but it will be fine to add to recipes). Here’s a nice tutorial on how to freeze wine and ten more ways to use leftover wine.