Tartrates are crystals of tartaric acid salts that can form in wine, most commonly potassium bitartrate. They may appear as clear or pale crystals on the cork or at the bottom of a bottle, especially after the wine has been chilled. They are harmless and do not indicate spoilage or poor quality.
Tartaric acid is a naturally occurring acid in grapes and wine. When wine is cold, potassium bitartrate becomes less soluble and can crystallise out of solution. The crystals may form during storage or after bottling, particularly when the wine has not been cold-stabilised. Temperature changes can encourage their formation.
Tartrate crystals can resemble small shards of glass, sugar crystals or grains of sand. In red wine they may be coloured by pigments and appear darker. If crystals are present, they can be left in the bottle by pouring carefully or removed by decanting or straining when appropriate. They are not harmful if accidentally consumed, although their texture may be unpleasant.
Tartrate crystals are salts of tartaric acid. Wine sediment may also include precipitated tannins, pigments, yeast cells or other particles. Both can occur naturally during wine maturation, but they have different compositions and causes.
Example: a chilled bottle of white wine may develop clear crystals on the underside of the cork or at the bottom of the bottle. These are commonly called “wine diamonds.”
Cream of tartar is potassium bitartrate, the same salt that can crystallise in wine. In the kitchen it is used as an acid ingredient, including to help stabilise whipped egg whites and in some baking powders.
Chef’s note: tartrates are a natural and harmless occurrence. Explain them calmly to guests and distinguish them from glass fragments or signs of spoilage.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
