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g WINE g rAoKw i n g rape M ING and heavily super-saturated (using powdered KHT) sample and calculates the change in conductivity to infinite time using a proprietary program. Common variables include the temperature of the test, although it is usually run at -4ºC. This method aims to avoid application problems of the "UC Davis Conductivity Test" by selling the method with its own instrumentation and removing as many variables as possible. This test is considered "proprietary" and is generally run on one brand of equipment (Stabilab brand), which also supplies its own pre-weighed capsules of standardized bitartrate powder. This test is used to allow electrodialysis companies to "dial in" the amount of treatment needed, and for that reason it was set up to be strictly controlled. C. "Mini Contact" Conductivity Test, Variation III: "Index of Tartrate Stability" (ISTC50) This is another "proprietary" conductivity test from Oenodia, specifically selected to confirm electrodialyzed wine stability. Again, the only variable is the temperature, although the recommended test is done at -4ºC. 145 Jordan Street • bitartrate (a process not subject to the kinetic challenges of the opposite direction) and its tendency to form crystals in cold-hold tests. This index is determined by measuring the conductivity of a wine twice. The sample is tested without added excess powdered tartrate crystals and then a second sample is tested with a spike of 4 g/L powered bitartrate. The samples are warmed, and as any added tartrate crystals dissolve, the conductivity increases more than in the unspiked sample. The difference in conductivity between the two samples at 20ºC is used in the Wurdig or the Maujean equation to calculate the Degree of Saturation (in ºC). This value, "Tsat," estimates the temperature at which the wine is capable of dissolving additional tartrate. Additional empirical relationships are used to estimate the temperature of instability (the temperature at which this wine would be predicted to precipitate crystals) using the degree of saturation. This is a conductivity-type test, but it does not use super-saturation of KHT powder to promote precipitation. Rather, it uses precisely quantified added KHT levels, said to be just enough to facilitate production of nuclei in what should usually be a stable, electrodialyzed wine. The precision is needed because the exact impact of this added bitartrate on the conductivity is subtracted from further calculations. The amount of spiked powdered tartrate used (0.5 g/L) is the "50" in the "ISTC-50." There is also use for ISTC-75 mentioned in literature. The rationale for the complexity of this particular degree of spiked bitartrate addition was to design a predictive test that would correlate to a three-day cold-hold at -4ºC. The justification for this test is that electrodialyzed wines fail other conductivity test methods; one proposed explanation involves a pH shift that artificially drops the conductivity value. D. Degree of Saturation (Tsat) Lab Testing Category III: Chemical solubility methods The Degree of Saturation is a predictive index formed by the evaluation of hundreds of wines to determine the relationship between the ability of the wine to dissolve/absorb additional San Rafael, CA 94901 • 415-457-3955 • Fax 457-0304 A predictive index based on solubility chemistry. Most cellar methods rely on the reduction of concentration of the • www.boswellcompany.com pr actica l win ery & vin eya rd APRIL 20 13 61