Have you ever found little "diamonds" or such in your wine? We have heard the below comments about aged wine and even some about our own wine. "There is sand in the bottom of the bottle...The wine is sparkly... What are the crystal formations on the cork?"
Of course they all refer to the tiny tartrate crystals which can sometimes be found in wines and on our corks. Tartrates is the general term used by winemakers to describe the harmless crystalline deposits that separate from wines during aging. Although tartrates precipitated in red wines usually take on some red or brown coloring from absorbed wine pigments and are commonly regarded as mere sediment, in white wines hey can look alarmingly like shards of glass to the uninitiated.
This common misconception has led to the some overuse of cold stabilization by the industry to the point of losing wine flavor and body. So when you do see tartrate crystals it is actually a sign of less-manipulated wine. The modern volume wine industry has, for the most part, decided that removing tartrates by stabilization is preferable to consumer education. The European culture, when confronted with wine "diamonds" in their wine bottles, usually accept the wine as high quality. In the U.S. this is not always true.
Tartaric acid (HTa) is the most important acid found in grapes and wine as it plays a major part in determining the taste of the wine. In JARVIS wines Tartaric acid (HTa) of about 4 grams per liter is typical. Tartaric acid is also the principal component of the mixture of acids and salts that constitute the wine's buffer system and maintains the stability of its acidity and color.
It is interesting to note that although it is a natural organic acid, tartaric acid, is rarely found in plants. The grape and tamarind are the only fruits of significance which are tartrate accumulators. The amount of tartaric acid found in grapes and wine can vary by varietal, soil, and weather. Cooler climates in general favor higher concentrations of tartaric acid.
Tartrates tend to separate from wines because tartaric acid is less soluble in solutions of alcohol and water such as wine than it is in plain water or grape juice. Experience shows that about half of the tartrate soluble in grape juice is insoluble in wine. The problem in wine is that the tartrate may remain in a soluble state in the complex wine mixture only to crystallize at some unpredictable later time.
Tartrate instability was recognized as a problem only in the 19th century when, with greater wine production and standardization of bottle production, bottle-aged wines first became common. Previously wine were not expected to be perfectly clear, although some would routinely be strained. Today producers of most modern wines, particularly all inexpensive white wines, believe that their customers expect brilliantly clear liquid to emerge from the bottle, no matter how long it has been there.
By filtration, it is relatively easy to ensure perfect clarity immediately prior to bottling. Historically wines were stabilized against tartrate precipitation by letting the cellar cool to temperatures near or below freezing during the winter. Low temperatures for 3 to 4 months would usually remove so much tartrate that further precipitation was unlikely. The modern equivalent is to use refrigeration to chill the wine before bottling. When the wine is cooled down to a temperature of 30˚F the tartrates will cling to the sides of the container or simply fall to the bottom.
So the next time you see wine diamonds in the bottom of your wine bottle or attached to the cork you'll know there is some history behind it and chances are you've got quality wine.