Have you ever purchased a white wine and noticed crystals in the bottom of the bottle or a red wine that has crystals on the bottom of the cork? Many consumers look at this as sediment, but it is not wine sediment. It is potassium bitartrate. A natural grape acid found in wines. These crystals form when wine is chilled, and the acid molecules crystalize and fall out of solution. If you have ever used cream of tartar in your kitchen, then you are familiar with these crystals.
These crystals are completely harmless and a generally a sign that the wine has not been over manipulated in the winery. Most wines go through a process called cold stabilization that promotes this bitartrate crystallization in the winery in stainless steel tanks. In order to do this the wine is chilled to 30 degrees F and left there for several weeks. Once the crystals have formed, the wine is filtered off the crystals and prepared for bottling. Another method to prevent crystallization involves using a blend of cellulose polymers added to the wine to prevent the crystallization. These polymers disrupt the surface of the crystals preventing crystallization.
Many winemakers, including ours, skip this step, feeling that the process takes away from the delicate nuances and flavors. In addition, there are some concerns on the environmental impact of chilling large tanks and volumes of wine for such a long period of time. The chillers are energy hogs and pull a lot of power from the grid to keep tanks at 30 degrees. Many of these wine tanks are outside and the chillers must work hard to combat the elements.
Winemakers are also generally against using too many additives in their wine. Using the cellulose polymers is an acceptable way to stabilize white wine, but our winemaker just does not like adding outside products to our natural wines. Our philosophy is to keep our wines as natural as possible.
So, if you get a bottle of wine with crystals in it, consider yourself lucky. We like to call those wine diamonds. This is generally a sign of a high-quality, low production wine that is sure to please. The crystals are totally harmless.