Potassium calcium tartrate

In wine, simple salts are dissociated into TH and T ions. The last two tartrates (Figure 1.10) share the property of forming and remaining stable at a pH of over 4.5. On the other hand, in terms of solubility, they differ in that potassium calcium tartrate is highly soluble, whereas the tartromalate is relatively insoluble and crystallizes in needles. The properties of this mixed salt may be used to eliminate malic acid, either partially or totally. Table 1.11 shows the solubility, in water at 20° C, of tartaric acid and the salts that cause the most problems in terms of crystalline deposits in wine. 

Fig. 1.10. Structure of (a) double potassium calcium tartrate and (b) calcium tartromalate...

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

Table 6 Hsts the leavening acids and the corresponding rates of reaction. The leavening acids most frequently used iaclude potassium acid tartrate, sodium aluminum sulfate, 5-gluconolactone, and ortho- and pyrophosphates. The phosphates iaclude calcium phosphate [7758-23-8] CaHPO, sodium aluminum phosphate, and sodium acid pyrophosphate (66).

The chemical reactions involved in tartaric acid production are formation of calcium tartrate from cmde potassium acid tartrate. 

Fig. 4. Manufacturing process for (R-R, R -tartaric acid (TA) and its salts, calcium tartrate (CT) and potassium tartrate (PT).

The acid potassium or calcium tartrates are found in many plants but the chief source of tartaric acid is the impuie acid potassium salt, which separates out as wine-lees, or argol from grape-juice in process of fermentation. 

O. Katsuki et al, KogyoKayaku 31(3), 131-7(1970) CA 78, 6073(1973) (Combustion preventive chemicals for coal mine expls. I. Organic compds. Out of 60 compds tested only ammonium, sodiym or potassium oxalate, sodium or potassium formate, and calcium tartrate were effective)... 

Newly fermented wines are usually supersaturated with potassium bitartrate. Wineries routinely remove the excess potassium bitartrate in wines by refrigeration or ion exchange procedures. These steps are necessary to obtain a wine free of tartrate deposits after bottling. Calcium may also combine with tartrates which contribute to the deposits in wines. Generally, the stabilization practices for potassium bitartrate are sufficient to remove calcium tartrate from wines. 

In addition to deposits of crystalline potassium bitartrate, infrequent calcium tartrate deposits occur in wines. The calcium level of carefully produced wines is seldom high enough to cause stability problems. Occasionally, however, wines may extract calcium from improperly prepared filter materials. Prolonged storage in uncoated concrete tanks also will release calcium into wine. 

Tartaric Acid. Quantitative measures of total tartrate are useful in determining the amount of acid reduction required for high acid musts and in predicting the tartrate stability of finished wines. Three procedures may be used. Precipitation as calcium racemate is accurate (85), but the cost and unavailability of L-tartaric acid are prohibitive. Precipitation of tartaric acid as potassium bitartrate is the oldest procedure but is somewhat empirical because of the appreciable solubility of potassium bi-tartrate. Nevertheless, it is still an official AO AC method (3). The colorimetric metavanadate procedure is widely used (4, 6, 86, 87). Tanner and Sandoz (88) reported good correlation between their bitartrate procedure and Rebeleins rapid colorimetric method (87). Potentiometric titration in Me2CO after ion exchange was specific for tartaric acid (89). 

Manufacture. The chemical reactions involved in tartaric acid production are formation of calcium tartrate from crude potassium acid tartrate, formation of tartaric acid from calcium tartrate, formation of Rochelle salt from argols. and formation of cream of tartar front tartaric acid and Rtxhelle salt (RS) liquors... 

It can precipitate as potassium hydrogen tartrate (KHT) or as calcium tartrate (CaT), the latter being practically insoluble in aqueous solutions. Their equilibrium solubility varies with temperature, pH, and alcohol content, while the presence of a few wine components, such as polysaccharides and mannoproteins, may hinder spontaneous nucleation even if the solution is supersaturated. From Figure 14 that shows the equilibrium tartaric acid-dissociated fractions versus pH and ethanol volumetric fraction (Berta, 1993 Usseglio-Tomasset and Bosia, 1978), it can be seen that in the typical pH range (3 4) of wines KHT is predominant. As temperature is reduced from 20 to 0°C, KHT solubility in water or in a 12% (v/v) hydro-alcoholic solution reduces from 5.11 to 2.45 kg/m3 or from 2.75 to 1.1 kg/m3, respectively (Berta, 1993). Each of these data also varies with pH and reaches a minimum at the pH value associated with the maximum concentration of the hydrogen tartrate anions. For the above-mentioned solutions, the solubility minimum shifts from pH 3.57 to pH 3.73 as the ethanol content increases from 0 to 12% (v/v) (Berta, 1993). 

Even in this case, the use of a hybrid process combining NF, IE, and ED appears to improve the economics and performance of the tartaric stabilization of wines. For instance, Ferrarini (2001) proposed to split raw wine into a retentate and permeate by NF. The permeate, being richer in minerals, was processed by using in sequence cationic and anionic exchange resins and ED to reduce its potassium, calcium, and tartrate ion contents. By recombining the de-ashed permeate with the NF retentate, Ferrarini (2001) asserted to obtain a stabilized wine retaining almost all the flavor and aroma compounds originally present in raw wine. 

Another method of acid amelioration, used to avoid water amelioration, is the addition of calcium salts for the purpose of substituting calcium for potassium ions. The resulting calcium bitartrate salts, being less soluble, increase the precipitation of bitartrate. This raises technical problems, one being that if the malo-lactic fermentation should take place subsequently, the wine may contain insufficient acidity of any kind. Another is that calcium tartrate precipitates slowly and in more finely divided form, often causing persistent hazes that are hard to remove. Often, too, this precipitation is delayed, leading to the presumption that the wine is tartrate stable. Only after it is bottled, the brilliant and supposedly stable wine may develop a delayed calcium tartrate haze and even a deposit. The calcium salt method in a refined form is used considerably in Germany but rarely here. 

L-Tartaric acid is an abundant constituent of many fruits such as grapes and bananas and exhibits a slightly astringent and refreshing sour taste. It is one of the main acids found in wine. It is added to other foods to give a sour taste and is normally used with other acids such as citric acid and malic acid as an additive in soft drinks, candies, and so on. It is produced by acid hydrolysis of calcium tartrate, which is prepared from potassium tartrate obtained as a by-product during wine production. Optically active tartaric acid is used for the chiral resolution of amines and also as an asymmetric catalyst. 

The cardiac toxicity of antimony has been explored in cultured myocytes (26,27). Potassium antimony tartrate disrupted calcium handling, leading to a progressive increase in the resting or diastolic internal calcium concentration and eventual cessation of beating activity and cell death. An interaction with thiol homeostasis is also involved. Reduced cellular ATP concentrations paralleled toxicity but appeared to be secondary to other cellular changes initiated by exposure to antimony. 

Commercially, L-(- -)-tartaric acid is manufactured from potassium tartrate (cream of tartar), a by-product of wine making. Potassium tartrate is treated with hydrochloric acid, followed by the addition of a calcium salt to produce insoluble calcium tartrate. This precipitate is then removed by filtration and reacted with 70% sulfuric acid to yield tartaric acid and calcium sulfate. 

Lees —The solid matter deposited in the fermentation vats and casks at the end of the primary fermentation is termed lees. It consists of impure hydrogen potassium tartrate mixed with yeast and other organic substances, and when mixed with water is extremely difficult to filter unless it has been previously subjected to steam heat for some time to destroy its slimy, colloidal nature. The lees from plastered wines contain calcium tartrate instead of the potassium salt, consequently it is not of much value for the manufacture of tartar. 

Tartaric Acid%—Tartaric acid is manufactured from tartar by dissolving it in water and adding whiting chalk until effervescence ceases, the solution being stirred mean while and heated by steam. Calcium tartrate and neutral potassium tartrate are thus formed. The potassium tartrate... 

---