Diamonds May Not Be a Wine's Best Friend
Winter is a bit of a slow time for the winemaker. The grapes have been harvested, the press has been cleaned and put away, and the wine has been made. That means my job is done, right? Well, it’s a little easier right now and not as frantic, but certainly not done. Right now, all the wines we made from the 2021 harvest are aging. Whites are aging in stainless steel tanks and reds are aging in oak barrels. But there is another process going on for the white wines: cold stabilization.
To explain this, we need to look at the grapes. All wine-making grapes have naturally occurring tartaric acid in them. Much like citric acid gives lemons and limes their tartness, tartaric acid gives the wine its own unique tartness. That tartness is desirable and important for balance in the finished wine. However, the wine can only hold so much tartaric acid, or tartrates, in suspension. If there is too much in the solution, it will start to precipitate out and form crystals. These crystals are affectionately referred to as wine diamonds. The cold stabilization process forces the wine to “give up” its excess tartrates. We do this by chilling the wine down to about 30°F for about 2-3 weeks. This causes the excess tartaric acid to solidify out of the solution. This process is mostly cosmetic for the wine, it does not change its flavor or aromas. If cold stabilization did not happen, or did not finish, you may find wine diamonds in the bottom of the bottle you just pulled out of the fridge. If you do not know what they are, you might think that there was something wrong with the wine. If you do find a bottle with some crystals in it, rest assured that it is safe to drink. The tartrates themselves do not taste like much but are a little gritty and not very pleasing texture-wise. Pour the bottle of wine slowly to avoid getting them in your glass or pour the wine through a strainer.
Wine diamonds can happen in both red and white wine, but we typically only cold stabilize the white wines. One of the biggest reasons is that white wines are ready to bottle sooner than red wine. Tartrates will precipitate out naturally over time. For a glass of red wine, this means that as they are aging in their barrels, they are releasing their wine diamonds and one year or so is usually plenty of time for tartrates to solidify. Another big reason is that white wines are served chilled, and chilling releases the tartaric acid crystals. A red wine that is never chilled may never have its excess tartaric acid precipitate out of solution.
Although winter is kind of a slow boring time in the cellar, it is the best time for cold stabilization. All this cold weather means that our tank chiller doesn’t have to work so hard to keep the wine at the right temperature. But it also means that I’m a lot colder while I work.