Have you ever purchased a bottle of wine and upon opening it discovered tiny red or white crystals stuck to the bottom of the cork or floating at the bottom of the bottle or in your glass?
Naturally, your initial reaction might be to question the quality of the wine or assume that something is terribly wrong with it.
Did glass somehow get in the bottle? Is it salt? Maybe sugar? Answer: No, and those crystals are harmless. The wine is perfectly fine to drink. The crystals are called tartrates and they are a by-product of tartaric acid and potassium binding together. Both are naturally found in grapes. The scientific term is potassium bitartrate, the equivalent of cream of tartar found in your kitchen cupboard.
This acid creates the tartness in the wines flavor profile and it’s an important part of managing the PH levels which impact color, aroma, flavor, stability and ageability.
There’s a lot of science behind PH levels and without getting too deep, we’ll stick to what you’re seeing in the bottle. Among some industry professionals the crystals are called wine diamonds or in Germany they are called weinsteins or wine stones.
As wine ages tartrates are a natural result and tartaric acid crystals are formed when a wine goes through the cold stabilization process. This process of chilling the wine down to approximately 35 degrees is done so the tartrates can be filtered out before bottling to give the wine the perfect visual appearance that most consumers expect.
It’s really a matter of preference; many wineries that employ minimal intervention philosophies will not cold stabilize or filter. The crystals are more commonly found in white or rosé wines, reds tend to have lower tartaric acid levels and it’s often mitigated during the barrel aging process.
While the crystals are harmless and tasteless, think of it as water freezing and forming crushed ice, it’s still just water, but the gritty mouthfeel of tartrates isn’t exactly pleasant. You can easily filter them out by decanting the wine through a fine mesh screen or cheesecloth.
For a lot of seasoned wine drinkers the crystals are viewed as a sign of higher quality because the wine hasn’t been overly manipulated and left to age in its most natural state. With or without, the wine is fine! Cheers!