Hi folks, I am seeing something that I thought was really only a problem with beer making - specifically that when I put my 2003 French colombard in the fridge it gets cloudy. Just like a chill haze in beer. This wine is crystal clear at room temperature, and was filtered prior to bottling, but definitely develops a haze when chilled.
Anyone seen this before? or have an idea what might be going on? thanks - steve in vancouver
Steve, Grapes contain tartaric acid potassium. Potassium reacts with tartaric acid and forms a material called potassium bitartrate. Potassium bitartrate is a clear, crystalline material. Cooks usually refer to potassium bitartrate as cream of tarter, but most winemakers call this material "tartrate." Potassium bitartrate has several interesting physical properties. (1) Only small quantities of this material can be dissolved in grape juice. (2) After grape juice ferments and alcohol accumulates, even less potassium bitartrate is soluble in the water-alcohol mixture. (3) The quantity of potassium bitartrate dissolved in wine is strongly dependent upon temperature, and cold wine cannot hold as much potassium bitartrate as warm wine.
Generally, grape juice contains all the potassium bitartrate it can hold when the grapes are picked. Alcohol begins to accumulate when the grapes are fermented. As the alcohol concentration increases, the new wine becomes saturated, and potassium bitartrate precipitates out of the wine. As fermentation continues, more alcohol is produced, and more tartrate is forced to precipitate out of the wine. So, new wine is over saturated with potassium bitartrate when fermentation is complete, and the tartrate continues to drop out of the solution. However, tartrate precipitation is very slow at normal cellar temperatures, so potassium bitartrate causes serious long-term stability problems for the wine industry.
The following example illustrates a common tartrate stability problem. A new white wine is clarified and aged for several months. The wine is then filtered with a 0.45-micron membrane and bottled. The newly bottled wine is clear and bright, but the wine is still nearly saturated with potassium bitartrate. Ultimately, a consumer puts a bottle of this wine into a refrigerator for a few hours before it is served. The wine cools rapidly in the refrigerator, and potassium bitartrate precipitates out of the cold wine. (See property number three above).
As tartrate drops out of solution, suspicious looking crystals are formed in the bottle, or haze forms. Tartrate hazes are very unsightly, and sometimes the consumer mistakes the tartrate crystals in the bottle for glass particles. In any case, the consumer is unhappy, and the winemaker is embarrassed. All commercial white and blush wines are cold stabilized (held just above freezing for several days) sometime during the winemaking process to remove the excess tartrate material before the wine is bottled.
Lum, thanks for your thoughts - my assumption as well was that it could only be tartrate, but I was expecting little crystals not general cloudiness. do you think if I chilled the bottles for several days the tartrate would precipitate to form crystals - or am I stuck with cloudy wine.
by the way the taste is fine. steve
I'm not sure Steve. I do know that hazes tend to form when a wine is cooled down quickly and that crystals tend to grow when the wine is cooled down very slowly.
WOW !!! I don't even make wine and I found that very informative. Great response !!!
Thanks,
Duke
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