Wine Diamonds: A Growing Controversy
While in one of our favorite neighborhood restaurants and enjoying a bottle of red wine with dinner we encountered the rare find of little crystals in the bottom of our wine bottle referred to as “wine diamonds”. Upon my bringing the anomaly to the attention of our hostess she went in the back and Googled “crystals in my wine glass” and proudly announced that they were actually a sign of a good wine and that it was nothing more than sugars that separated from the wine.
She was not entirely correct. Let’s start with a cursory look at very basic wine chemistry (incidentally, I flunked high school chemistry based on the “Why would I ever need to know that kind of stuff?” teenage reasoning and wisdom I possessed back then. Oh, the irony…).
All wines, red and white, contain acids. The dominant acids found are malic and tartaric acid. During the fermentation process the malic acid is converted to a lactic acid, but the tartaric acid remains in the wine helping to maintain a balanced pH. When the wine is subjected to cold temperatures the tartaric acid combines with naturally occurring potassium in the wine and forms potassium bitartrate crystals referred to as wine diamonds which may be found growing to the cork or swimming about in the bottom of the bottle .Tartrates are present in both red and white wine, but because the initial level of tartaric acid is lower in reds and more of it tends to separate naturally in the aging process, the formations of wine diamonds are less common in reds wines.
Most wines we buy today are clear and free of any sediment because most wineries go to great lengths to ensure a product that is virtually clear and visually pleasing. In order to prevent the formation of wine diamonds most wineries subject their products to a “cold stabilization” process prior to bottling where the wine is subjected to near freezing point temperatures for a week or longer. This precipitates the development of the crystals which adhere to the walls of the cask or tank and remain while the wine is removed. Though wine diamonds appear more frequently in whites than reds, commercial wineries will cold stabilize the reds as well.
“Wine diamonds are a sign of quality wine”. This is where our hostess erred again.
Some people will argue that the presence of wine diamonds indicates a quality wine because it means the wine has not been subjected to cold stabilization which conceivably changes the final pH and therefore alters the taste of the wine. This school of thought often belongs to those who also feel that cloudy wine is apt to taste better because it is unfiltered and would hold a more honest flavor.
However according to others, wine diamonds can also indicate a bottled wine that has been stored in near freezing temperatures where the acid and potassium bonding process has had the opportunity to recommence. Something as simple as shipping during the winter months where the wine is subjected to uncontrolled climate is an example of how this might occur.
So are wine diamonds detrimental to wine? Whatever your feelings are towards them and regardless of how they arrived in your bottle, they are harmless. If you find them to be undesirable you can filter them out with a fine screen filter (using a paper filter is not recommended as the paper may impart some of its own pulpy flavor into the wine).
Or you could just ignore them and enjoy the wine.