2014 Eastern Winery Exposition: Tartrate Stabilization Part 2

Tom Payette spoke about tartrate stabilization, one of the things that winemakers do before bottling their wine. This is the process of removing the potassium tartrate that exists in wine. Personally, I love seeing crystals of potassium tartrate on a red wine cork or even clear crystals of potassium tartrate in white wine, where they are called wine diamonds. Girls do love diamonds, after all! But, they can be confused with shattered glass, so it has become standard operating practice to remove the potassium tartrate.
There are several factors that affect the solubility of potassium tartrate (KHT), or it's ability to stay in solution:

• KHT is more soluble in water than in alcohol, so the higher the alcohol content, the less soluble is KHT
• KHT is more soluble in the presence of colloidal materials, such as mannoproteins, pectins, and other polysaccharides
• KHT solubility is affected by the wine pH, KHT will precipitate out at its lowest solubility level at a pH between 3.4-4.0
• KHT solubility is affected by changes in the wine such as blending or fining
• KHT solubility is affected by temperature, the colder the temperature, the more insoluble the KHT

A conductivity test should be conducted before the tartrate stabilization. The high concentration of potassium ions are primarily responsible for the conductivity in wine. As potassium ions are taken out of solution the conductivity is lowered. A change of less than 5% in electrical conductance over the testing period is considered stable.² There are various methods of achieving tartrate stabilization including:

• Stabilization by cooling
• Stabilization by contact seeding
• Stabilization by electrodialysis
• Stabilization by the addition of Carboxymethyl Cellulose (CMC)
• Stabilization by the formation of meta-tartaric acid

Tom Payette spoke extensively on tartrate stabilization by contact seeding. A detailed description on how to conduct contact seeding can be found here:
Cold Stabilization by Contact Process by Dr. Murli Dharmadhikari.
One of the best books that I have seen on laboratory methods for wine is authored by Iland, Bruer, Edwards, Caloghiris and Wilkes called Chemical Analysis of Grapes and Wine: Techniques and Concepts 2nd Edition.
References:
1. Virginia Smith, Assessment of Cold Stabilization for Tartaric Acid in Wine, Penn State Food Science, Penn State Extension, October 3, 2012.
2. B., K. Fugelsang, B. Gump, and F. Nury, Wine Analysis and Production, Chapman & Hall, New York, 1995.