Alcohol in wine

Acids can be produced by the oxidation of aldehydes or primary alcohols. For example, the souring of wine results from the oxidation of the ethyl alcohol in wine to acetic acid ... 

One example of autooxidation you have experienced is the room-temperature oxidation of alcohol in wine. Within days and sometimes within minutes of opening a bottle of wine, the taste begins to deteriorate because of autooxidation. This converts the ethanol into acetaldehyde and to acetic acid, both of which taste bad. Wine lovers talk about letting the wine breathe after opening so apparently some oxidation actually helps the taste. Distilled vinegar is made by the intentional oxidation of the alcohol in fermented apple juice into acetic acid, which can then be distilled from the juice and pulp. 

RF McFeeters. Single injection HPLC analysis of acids, sugars, and alcohols in wine. Abstract of papers of the American Chemical Society, (22 August 1993), 206(1) 51, 1993. 

Fermentation of the sugar from grapes yields the ethyl alcohol in wine. 

Figure 1.14 Scheme of HPLC system with detectors UV-Vis and RI on-line used for simultaneous determination of organic acids, sugars and alcohols in wine... 

An enzymatic method for determining alcohol in wine is evaluated by comparison with a gas-chromatographic (GC) method. The same sample is analyzed several times by both methods with the following results (% ethanol). Enzymatic method 13.1, 12.7, 12.6, 13.3, 13.3. GC method 13.5, 13.3, 13.0, 12.9. Does the enzymatic method give the same value as the GC method at the 95% confidence level ... 

When the alcohol in wine changes into vinegar, there are two processes involved. The first one is relatively minor. Ethanol, the alcohol of beverages, reacts with oxygen to form acetic acid, a dilute solution of which we refer to as vinegar. This happens only to a very small extent, because the wine doesn t come into contact with much oxygen. What really causes wine to turn to vinegar is contamination with a bacteria called Acetobacter aceti. 

Without question the greatest challenge faced by the wine industry is rapidly mounting concerns over alcohol consumption excess consumption creates problems for society and human health. In addition, too much alcohol in wine can overwhelm flavour and... 

Methods—Refractometric. A rapid method for determination of alcohol in wines by refractive index was developed by Newton and Munro (1933). Use of their formula for the immersion refractometer determination of alcohol was found inapplicable to... 

The presence of isopropyl alcohol in wines has been the subject of some controversy. Bodendorf (1930), for example, demonstrated isopropyl alcohol in brandy, but his procedure was rather insensitive. 

Mannitol. Whereas mannitic fermentations are seldom a problem where sulfur dioxide, pure yeasts, and temperature control are employed, Martucci (1941) has reported them in Argentina. He recommended control of the must acidity, since a high pH also favored such spoilage. A complicated polaiimetric procedure for mannitol (a sugar alcohol) in wines was presented by Salani (1937). Formation of mannite during dialysis of musts at low temperatures (8° to 10° C. (46.4° to 50° F.)) in the presence of chloroform was reported by Barbera (1933b) (possibly owing to enzyme action). 

Etienne, A. D. 1950. Determination of alcohol in wines and liqueurs. J. Assoc. Offic. Agr. Cherniy 88, 1015-1020. 

Fabre, J.-H., and Br5mond, E. 1935. A study of different methods of estimating alcohol in wines (transl.). Congr. intern, tech. chim. ind. agr., Bruxelles 8,308-315. 

Zimmermann, H. W. 1949. Determination of alcohol in wines by the dichromate method. Proc. Wine Tech. Conf., Davis 1949, 107-109. 

Figure 8.87 Separation of organic adds, carbohydrates, and alcohols in wine using refractive index detection. Separator column HPX-87 H column dimensions 300 mm x 7.7 mm i.d. column temperature 65 °C eluent 6S mmol/L H2SO4 flow rate 0.8 mlVmin detection refractive index injection volume 5 pU sample wine...

In routine use in more than 50 sites in Erance is the NIR measurement of alcohol and sugars in wine and distilled liquors [7]. The concentration of alcohol in wine was determined by Kaffka and Norris as early as 1976 [8]. The accuracy of their calibration is reported as better than 0.1% by volume at 11 to 17% alcohol using transmittance as the mode of detection. Sucrose in wine has also been investigated. An accuracy of 0.2% is achieved with a calibration for sucrose levels of 0.8 to 8.8%. 

Actually, it was regarded as a useful stimulant in the nineteenth century and at one stage it was even available in over-the-counter medications. A Corsican chemist named Angelo Mariani made the discovery that the alcohol in wine extracted the cocaine from coca leaves and put the result, Vin Mariani, on sale. He understood the value of publicity, sending bottles to famous people and getting them to endorse his product. Jules Verne, H.G. 

Several experiments clearly indicate, however, that the degradation of amino acids is not the only pathway for forming higher alcohols in wine. In fact, certain ones, such as propan-l-ol and butan-l-ol, do not have amino acid precursors. Moreover, certain mutants deficient in the synthesis of specific amino acids do not produce the corresponding higher alcohol, even if the amino acid is present in the culture medium. There is no relationship between the amount of amino acids in must and the amount of corresponding higher alcohols in wine. 

Higher alcohol production by yeasts appears to be linked not only to the catabolism of amino acids but also to their synthesis via the corresponding ketonic acids. These acids are derived from the metabolism of sugars. For example, propan-l-ol has no corresponding amino acid. It is derived from a-ketobutyrate which can be formed from pyruvate and acetyl coenzyme A. a-Ketoisocaproate is a precursor of isoamylic alcohol and an intermediary product in the synthesis of leucine. It too can be produced from a-acetolactate, which is derived from pyruvate. Most higher alcohols in wine can also be formed by the metabolism of glucose without the involvement of amino acids. 

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