HANNA HI 83748-01

Tartaric acid and tartrate play an important role in the stability of wines. They can be present in wine and juice in various forms, like tartaric acid ( H2T) , potassium bi-tartrate ( KHT) or calcium tartrate ( CaT) . The ratio of these depends mainly on the pH of the wine. The percent of tartrate present as bitartrate ( HT-) is maximum at pH 3.7.

The formation of crystalline deposits ( tartrate casse) is a phenomenon of wine aging that does not meet customer acceptance. It is therefore important to test for, and to reduce the potential of bottle precipitation. For example, by adjusting the pH of the wine, winemakers can significantly influence the potential of casse formation.

Potassium concentrations in wine can range from 600 to 2500 mg/ L ( ppm) in certain red wines. Although the potassium bi-tartrate is soluble in water, alcohol and low temperatures decrease its solubility. Especially during the alcoholic fermentation potassium bi-tartrate becomes increasingly insoluble resulting in super-saturation and precipitation. The KHT stability can be restored by chilling ( with or without seeding) . Wines with initial pH values below 3.65 can show a reduction in pH during cold stabilization because of generation of one free proton for each KHT precipitated. The pH may drop as much as 0.2 pH unites. For wines at higher pH than 3.7, the pH shifts to a higher pH.

Calcium concentrations can range from 6 to 165 mg/ L ( ppm) and may complex with tartrate or oxalate to form crystalline precipitates. Calcium tartrate instabilities occur normally from 4 to 7 months after fermentation and are temperature independent.

Sulphates, proteins, gum and polyphenols can form stable complexes with tartrate thus inhibiting casse formation. The complexes are mainly between polyphenols and tartaric acid in red, and proteins in white wine. This explains why, as pigment polymerization occurs, the holding capacity of tartaric acid diminishes, resulting in delayed casse. The sulfate instead does not complex with potassium from 50% in white wines up to 100% in red ones.

Tartaric acid concentrations in wine range normally from 1.5 to 4.0 g/ L. This acid concentration may not be confused with total or titratable acidity of wines that are often expressed in tartaric acid content too. Although it is the tartaric acid that is the predominantly present acid ( up to 60% of the total acidity) , others like malic, citric and several volatile acids do give a significant contribution total acidity.

Order Information:
HI 83748-01 ( 115V) and HI 83748-02 ( 230V) are supplied with sample cuvettes and caps ( 2) , reagents for 5 tests ( HI 83748A-O, HI 83748B-O) , 200 µ L automatic pipette with Instruction Sheet, plastic tips for 200 µ L automatic pipette ( 2) , 5 mL syringe with tip, cuvette cleaning cloth, 12 VDC adapter, batteries, instructions, instrument quality certificate and rugged carrying case.