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6 4 V I N E YA R D & W I N E RY M A N A G E M E N T | J u l y - A u g 2 015 w w w. v w m m e d i a . c o m artrate stabilization in the concluding stages of the winemaking process helps prevent tartrate pre- cipitation in finished wine. There are several methods to determine tartrate stabil- ity, each having advantages and disadvantages. Tartaric acid and its vari- o u s f o r m s a r e n a t u r a l l y found in grapes and wine. The principal form of tar- taric acid present in wine is potassium bitartrate, com- monly abbreviated as KHT. As grapes develop on the vine, potassium from the soil moves into the ripening fruit and forms soluble KHT. S i n c e p o t a s s i u m u p t a k e g r e a t l y d e p e n d s o n t h e characteristics of the soil in which grapes are grown, dif- ferent types of wines show a large variation in KHT. The presence of KHT in wine can lead to its pre- cipitation, or formation of crystalline deposits, in a fin- ished product. KHT crystals are the visible particles that may appear at the bottom of wine bottles during stor- age, export or when chilled before consumption. KHT is, in fact, not harmful to a wine o r i t s c o n s u m e r s ; s o m e wine enthusiasts may even view KHT crystals as an indi- cator of high-quality wine that has not been overpro- cessed. Today, monitoring KHT levels in wine is simply a matter of aesthetics to ensure tartrate crystalliza- tion doesn't occur once the wine is poured and ready to drink. The process of removing KHT as part of the winemak- ing process can be referred to as cold stabilization or tartrate stabilization. A wine BY LAURA CHARTIER + There are several methods for deter- mining tartrate stability, each with pros and cons. + The presence of KHT in wine can lead to formation of crystalline deposits in the finished product. + A wine is considered stable when enough KHT crystals have been removed to ensure crystals won't form in a fin- ished wine. + The freeze test is simple to perform, but is time intensive and subjective in deter- mining the presence and quantity of KHT crystals. + The conductivity test requires a greater investment of equipment and frequent measurements, but provides a faster and more objective stability measurement. AT A GLANCE Conductivity testing and freeze testing have benefits and drawbacks Photo: Tom Johnson