Cold stability

Biologically active particles and fractions may be filtered from fluids using ultrafilters. This process is used extensively by beer and wine manufacturers to provide cold stabilization and sterilization of their products. 

To prevent the formation of wine crystals during the bottling process, winemakers use a method known as cold stabilization. By lowering the temperature of the wine to 19-23°F for several days or weeks, the solubility of tartrate crystals is lowered, forcing the crystals to sediment. The resulting wine is then filtered off the tartrate deposit. The temperature dependence of the solubility of potassium bitartrate is readily apparent in the following comparison while 162 ml of water at room temperature dissolves 1 g of the salt, only 16 ml of water at 100°C are needed to solubilize the same amount of saltJ l Recent developments employ a technique known as electrodialysis to remove tartrate, bitartrate, and potassium ions from newly fermented wine at the winery before potassium bitartrate crystals form. 

Steiner, K. and Stocker, H. R. (1969). [Polyphenols and cold stability of beer.] Polyphenole und Kaltestabilitat des Bieres. Tageszeitung fuer Brauerei 66,550. 

Holden, C., Combined Method for the Heat and Cold Stabilization of... 

Even when no additive is used in winemaking, the necessity for small-lot trial before production scale operation is apparent. Because a high percentage of wine is consumed only after chilling, and because chilling may accelerate the precipitation of potassium acid tartrate, ill-defined colloids, anthocyanin-tannin polymers, proteins, etc., simple cold stabilization by refrigeration in the winery may irreversibly alter the product and its eventually-perceived quality level. It often happens, especially in heavy-bodied red varietal wines, that a dark, amorphous precipitate may form in the bottle over several years. Usually tannoid,... 

The conventional tartaric stabilization techniques applied in the wine industry are based on two opposite principles. One is aimed at heightening HT- and T2- precipitation by reducing wine temperature and leads to the so-called cold stabilization technique. To accelerate nucleation, wines are seeded with exogenous KHT crystals, cooled and kept at —4°C for 4-8 days... 

A number of sensory tests have so far revealed no difference in the organoleptic properties of ED- and cold-stabilized wines (Bach et al., 1999 Cameira dos Santos et al., 2000 Goncalves et al., 2003 Paronetto et al., 1977 Riponi et al., 1992 Wucherpfennig and Krueger, 1975). 

Bitartrate Stabilization. Potassium and tartaric acid are natural constituents of the grape. Wine content of these constituents depends on a number of variables, not all well understood variety, vintage, and weather pattern degree of skin contact alcohol level bitartrate holding capacity of phenolic compounds and potassium binding capacity of the wine (30, 35). Most wines after fermentation are supersaturated solutions of potassium bitartrate. This compound is less soluble at lower temperatures, and, thus, lower temperatures will cause precipitation of bitartrate crystals. This lowering of temperature and subsequent removal of crystals by filtration is called cold stabilization. 

Clarification and Stabilization Combinations. Wine clarification may be combined with a stabilization step to minimize handling of the wine. This type of clarification, timing, and sequence vary from winery to winery. Some options used are, after fermentation, rack the wine off yeast lees, bentonite fine for heat stability and chill for cold stability, then diatomaceous earth filter to remove remaining yeast, bentonite, and tartrate crystals after fermentation, centrifuge the wine to remove yeast solids, then chill and add bentonite, and filter to remove yeast and add bentonite, chill, then pad filter to remove bitartrates and protein. 

Stabilization of wines is described by enologists as hot or cold stabilization. Hot stabilization is the term primarily used to describe removal of constituents such as proteins and colloidal materials that may precipitate out of the wine, particularly if the wine is subjected to elevated temperatures such as that used in pasteurizing. Hot stabilization doesn t mean actual use of heat to accomplish this. 

In cold stabilization, cold temperatures are used to cause precipitation of excess potassium acid tartrate out of the wines. If allowed enough storage time at very cold winter temperatures, this precipitation will take place. Under California winter conditions, this reduction of excess tartrates is very slow,... 

Refrigeration. At least one major winery minimizes the amount of wine movement necessary by cold stabilizing the wine at 28° F (-2.22° C) in a jacketed tank until laboratory evaluation shows the wine to be cold stable. The wine is allowed to warm to 30°-32° F (-1. ll°-0° C), then a slurry of bentonite, which has been soaked at least overnight in hot water, is added to the wine at the level prescribed by the previously described laboratory procedure. When the bentonite has settled to the bottom of the tank, the wine is racked off the bentonite lees and filtered to a holding tank. The wine is now ready for polish filtration and bottling. 

A number of small wineries in Washington do not have the refrigeration capabilities to achieve cold stability by chilling to 28° F (-2.22° C). These small wineries achieve cold stability by opening their wineries in the winter... 

Care must be taken when fining a sparkling wine with bentonite in order to preserve its foaming properties. Excessive use of bentonite for the fining of sparkling wine cuv es can produce a finished product that has a large bubble size and a poor bubble stability as a result of a reduction in both protein and peptide contents. Cold stabilization procedures cause both a precipitation of potassium bitartrate crystals as well as proteins because of the downward shift in pH. This precipitation of proteins... 

Traditional practices, such as white wine aging on lees in barrels for several months, confer the wine s tartaric salt stability, which dispenses them from any cold stabilization treatment. It has indeed been observed (Moine-Ledoux and Dubour-dieu 2007) that, in the Bordeaux wine-growing area, the majority of dry white wines aged on lees which are not stable in March after their first winter but become stable in June or July without any supplementary cold treatment (Table 5.1). In contrast, wines within the same crus which are not aged on lees systematically undergo cold treatment to obtain stability regarding tartaric salt crystallization. 

Vernhet, A., Dupre, K., Boulange L., Cheynier V, Pellerin R, Moutounet M. (1999a). Composition of tartrate precipitates deposited on stainless steel tanks during the cold stabilization of wines. Part I wMte wines. Am. J. Enol. Vitic., 50, 391-397. 

Cold Stability of Refined Sunflower Oil Sunflower oil waxes are fatty alcohol esters of fatty acids. Their melting point is around 75°C, and their solubility in the oil is low, leading to the appearance of turbidity in the refined oil with decreasing temperature. An oil s cold stability is usually assessed by means of the cold test (method AOCS Cc 7-25). Oils passing the cold test will remain clear—without the appearance of turbidity—after 5.5 hours permanence at 0°C. The solubility of waxes in sunflower oil is shown in Figure 21 as a function of... 

A.Vernhet, K. Dupre, L. Boulange-Petermann et al.. Composition of Tartrate Precipitates During... Cold Stabilization of... White Wines, Am. J. Enol. Viticult. 50(4), 391-397 (1999) Red wines, ibid., 398 03. 

After fermentation, wine becomes supersaturated with potassium bitartrate. The removal of this excess is necessary to avoid sedimentation after the wine is bottled. A cold stabilization technique where the wine is chilled just above its freezing point is generally used. Protective colloids, which prevent the crystaH ization of the excess potassium bitartrate make a wine resistant to cold stabilization even during prolonged refrigeration. In those... 

Solid fat contents are low, 37% at 10°C for normal olein and only 17% for super oleins (Table 3.7). At 25°C, most oleins are completely liquid. Super oleins fall into two categories. Those with iodine value below 61.5 have higher solids of 40-52% at 2.5°C and 31-42% at 5°C and those with iodine values exceeding 61.5 have much lower solids of 0.5-17% at 2.5°C and 0-16% at 5°C. (Tang et al. 1995), Improved cold stability can thus be expected with such oils. 

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