I’ve been thinking a lot about crystals lately, specifically Tartrate Crystals.  These are the fine, sand-like crystals you may find in the bottom of your glass after emptying the bottle into it, particularly in white wines.  In reds they are commonly found in the “sediment” in the bottom of the bottle and unlike white wines, no one seems to be incredibly concerned by their appearance in reds.  White wines however, can turn into a snow globe of these tiny particles if winemakers are not careful.  Which brings me back to the crystals themselves.

What are Tartrate Crystals?

The main type of acid in wine is called Tartaric acid.  This acid exists in wine to different degrees depending on the variety and climate in which the grapes are grown. Tartrate crystals are Potassium Bitartrate, which the lay person probably knows better as Cream of Tartar.  If you make a lot of Meringue you are probably very familiar with the powdered form.  Potassium Bitartrate forms when Potassium ions in the wine bind with tartaric acid molecules and precipitate out (fall out of solution).  The greater the alcohol content of the wine, the less stable these compounds are in the solution and the more readily they are able to fall out.  Cold temperatures speed up this process although it does occur naturally over time if the wine is allowed to age in the cellar for a lenghtly period.

What do Winemakers Need to do About Them?

This highly depends on to whom a winemaker is selling their wine.  These crystals are not harmful and do not represent anything wrong with the wine.  In many cases a wine that has the crystals is a sign that the wine was treated very gently in the cellar.  Most wineries will chill the wine down to extremely cold temperatures, 28 degrees F or so, to push the crystals to fall out in the tank so as not to alarm their customers.  Others will use electrodialysis to reduce the amount of Tartaric acid present in the wine.  The question is, however, what do winemakers need to do about these crystals.  Nothing really. All of this effort is to eliminate something that is purely cosmetic.  Every year millions of gallons of wine are put through some sort of cold stabilization process.  This uses a vast amount of energy, regardless of the method chosen, not to mention the cost of all that energy. PG&E did a study in 2008 which determined a full 25% of a winery’s total energy costs were directly related to cold stabilization and clarification.  I have often wondered if it would be cheaper in the long run to put out a Public Service Announcement (PSA) rather than continue to treat the wine. Maybe, just maybe this would help a few people understand a bit more about the winemaking process and how it is completely natural for this to happen.  Do I think winemakers will stop stabilizing? Most likely not but I do really love the ways that some wineries have chosen to address this issue.  My favorite is Jordan Winery in Sonoma.  You can read their PSA here.  They specifically address the fact that to completely stabilize a high end wine would result in lower body and flavor concentration and they choose to educate their customers rather than sacrifice the quality of the wine.    So here is my PSA.

Dear Wine Consumers,
   This Holiday season you may encounter some unknown substance that may resemble sand or small bits of glass in the bottom of your white wine glass.  Do not be alarmed. These are most likely harmless “wine diamonds” or Tartrate Crystals. If you are still concerned and want to find out for sure, perform this simple test.  Take the bits in question and put them into hot water and stir vigorously.  If they dissolve, they are harmless tartrate crystals.  Please go back to enjoying your wine.
Thank you for your time and remember, friends don’t let friends drink bad wine! Happy Holidays!