Have you ever heard of or encountered "wine diamonds?" I hope you haven't, because wine diamonds are the result of a short cut sometimes taken in wine making. Wine diamonds are actually crystals that form when tartaric acid, which is the primary acid found in wine, binds with potassium to form a compound known as potassium bitartrate. I know, I know...I am wine-geeking on you. I bring up the topic because we are getting ready to bottle Sunset and Moonlight, our two most poplular wines. Both go through a cold stability process shortly before bottling that is intended to keep the wine diamonds in our tank and not in your glass. Let me explain...
When wine is cooled, some of its chemical components bind with others and become insoluble. This is what happens when tartaric acid combines with potassium, forming potassium bitartrate. As the temperature of the wine drops, its ability to keep this combo in solution drops as well. In temperatures around 40 degrees...which is likely what your refrigerator is set to...tartrate crystals form. No one likes to take a sip of wine and get a mouthful of crystals. To ensure this does not happen with a wine you are likely to chill, we put our wine through a cold stability process meant to force the crystal formation while the wine is still in the tank. We chill the wine to approximately 30 degrees, saturate it with potassium bitartrate (the same stuff we are trying to take out), and circulate the wine for two hours. The addition of the potassium bitartrate draws out and binds the crystals that are forming naturally, and after a settling period of a few days, the heavy crystals drop to the bottom of the tank. We rack the clear wine off into another tank, and voila'...the tartrate crystals stay behind. Now you can put Sunset or Moonlight in your fridge and not worry about wine diamonds in your glass.
While the presence of tartrate crystals in wine does not alter the taste, the industry considers crystal formation in white wines to be a flaw. A white wine entered into a professional competition with wine diamonds will never receive a medal, no matter how good the wine tastes. Red wines, however, are not intended to be chilled. Because of this, most reds are not put through a cold stability process prior to bottling. If you prefer your reds with a bit of a chill, crystal formation may very well occur.
Whew...thanks for hanging with me on that incredibly interesting topic. I do love being a wine geek!
Until next time...Cheers!