Ethanol, content, wine

The presence of solutes other than ethanol might be expected to reduce the mole fractions of ethanol and water and influence the nonideality of the ethanol-water system. However, both Williams (1983), who modelled a batch wine fermentation, and Rottenbacher (1985), in ethanol sorption experiments with yeast pellets in a fluidized bed, established that the ethanol-water-yeast system behaves as if the water and ethanol content of the pellets were a simple ethanol-water solution supported by a solid matrix which influences neither mole fractions nor activity coefficients. 

In hot-climate viticulture it is a common practice to lower the high ethanol content of wines made from overripe fruit by partial dealcoholisation. This objective can be achieved by vacuum distillation, where the spinning cone column technique allows even more viscous liquids to be processed. Alternatively, a water-ethanol fraction can be separated from wine by reverse osmosis, followed by distillation of the water-ethanol permeate to yield high-grade ethanol and pure water. The latter will be added back to the treated wine. 

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). 

The ED-treated wines generally result to be completely stable once KHT and CaT have been selectively removed. Their basic characteristics (i.e., pH, acidity, sugar content, alcohol level), as well as taste, bouquet, and color, are practically unaltered, while their ethanol content, pH, and volatile acidity are reduced by less than 0.1% (v/v), 0.25 pH units, and 0.09 kg/m3 (expressed as equivalent H2S04), respectively (htpp //www.ameridia.com/html/wn.html). 

The colonies of this black mold are common on the walls and equipment of Tokaj cellars. C. cellare utilizes only volatile compounds which are present in the airspace of the cellar. Since it cannot tolerate ethanol contents above 2% (v / v), it never grows directly on the surface of wine, either sweet or dry. It has no direct impact on the quality of wine, although it beneficially influences the purity and humidity of the air in the cellar (Dittrich, 1977 Magyar, 2006, 2010). 

Extremely high or low temperatures can cause a fermentation to stick and it then becomes difficult to start again. Temperature also has an effect on the degree of extraction both from the skins and the seeds. Singleton and Esau (IS) reported that increasing the temperature and the ethanol content increased the extraction of seed tannins. Although these tannins are mostly precipitated, they could become an important part of some wines. 

In 1979, the California Department of Health lowered the minimum alcohol requirements for red table wines from 10.5 percent to the federal standard of 7 percent. This opened the door for the production of a completely new style of red table wine. Friedrich (13) calls this soft wine and it is made with ethanol contents of from 7 percent to 10 percent, usually... 

Secondary Fermentation. In addition to CO2, ethanol is formed during fermentation. Theoretically, 15.56 g/L glucose will yield 1.0 percent ethanol by volume. In practice, 16-17 g of glucose are needed. A sparkling wine in which 25 g/L sugar has been fermented will have an increase of ethanol content of 1.4-1.6 percent. The cuvee wine usually contains 11.5 percent or less ethanol before secondary fermentation to ensure complete fermentation. 

The shermat should be a clean, neutral white wine. The ethanol content of the shermat can be 12-16.5 percent. However, 14.5 percent is a good level. Lower ethanol wines are susceptible to acetification. At the upper limits, the flor yeasts do not grow or grow very slowly. The pH can be from 2.9 to 3.6. We have found 3.2 is a good average. At a lower pH, yeast develops very slowly. At over 3.4 pH, there is a risk of the growth of lactic acid bacteria. 

The growing conditions, weather, and day length, previously described, combine to form a set of conditions at harvest time that are often quite different from those found in California vineyards. It is sometimes necessary to delay the harvest of certain varieties to the upper limit of the desired soluble solids content to allow the total acidity of the fruit to be reduced to the desired level. This results in a wine with a relatively high total acidity and potentially with a high ethanol content as well. 

When alcoholic fermentation is too slow or when it stops, conditions are favourable for bacterial development. LAB ferment different quantities of sugars that have not been totally fermented by yeasts and produce acetic acid and D-lactic acid. This alteration is called Lactic disease" (piqure lactique) and is characterised by a high volatile acidity that depreciates the wine. If this volatile acidity exceeds the limit of 1 g/L, the wine is unmarketable (Lonvaud-Funel 1999). This spoilage also occurs in fortified wine where O. oeni, L. hilgardii, L. fructivorans and L. plantarum are active in spite of very high ethanol contents. 

Formation of the flor film is also affected by the ethanol content of the wine, the optimum value for which is 14.5-15.5 vol.% in fact, the film rarely forms above a 16.5 vol.% content. 

Oloroso wines are only obtained by oxidative aging, which is accomplished by fortifying the initial wine to an ethanol content of about 18 vol.% in order to prevent growth of flor yeasts. Under such conditions, oloroso wine acquires a dark colour by effect of the oxidation of phenol compounds. 

Nevertheless, the most studied ethanol effect is related to its capacity to modify solution polarity, thus altering the gas-liquid partition coefficient. An increase in ethanol content has been shown to decrease the activity coefficients of many volatile compounds in wine because of an increase in solubility (Voilley et al. 1991). Hartmann et al. (2002) showed a decrease in the recovery of 3-alkyl-methoxy-pyrazynes extracted with a divinylbenzene/carboxen SPME fibre from wine model systems when the ethanol content increased from 0% to 20%. Similarly, Whiton and Zoecklein (2000) reported that a small increase in ethanol content (from 11 % to 14%), in general, reduced the recovery of typical wine volatile compounds. Both of these studies suggest that increasing the alcohol content will reduce the release of volatile compounds from wines. 

Hermosm, I. (2003). Influence of Ethanol Content on the Extent of Copigmentation in a Cencibel Young Red Wine. J. Agric. Eood Chem., 51, 4079-4083. 

Reduction of ethanol content. The significance of ethanol for the overall flavor of alcoholic beverages was already mentioned by Williams and Rosser (23) and Rothe and Schroder (24). Sensory investigations of dealcoholized Sauvignon blanc, Chardonnay Semilion and Muskat Ottonel wines were performed by Fischer et al. (25). The authors established that the dealcoholization process reduced the fiuity attributes and the mouthfeeling of wines. 

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