Ethanol in wine

The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Write the Lewis structure for acetic acid, CH COOH, the carboxylic acid in vinegar formed when the ethanol in wine is oxidized. In the —COOH group, both O atoms are attached to the same C atom, and one of them is bonded to the final H atom. The two C atoms are bonded to each other. 

Experiment 42 The Determination of Ethanol in Wine by Gas Chromatography and the Internal Standard Method... 

Determination of Ethanol in Wines and Musts During Fermentation... 

At last the sensory part of ethanol in wine is important, it plays a major role on the volatility of flavors and in the interactions between aroma compounds and other components. 

A bottle of wine contains 12.5% ethanol by volume. The density of ethanol (C2H5OH) is 0.789 g/cm3. Calculate the concentration of ethanol in wine in terms of mass percent and molality. 

A.O.S.S. Rangel, I.V. Toth, Determination of ethanol in wines by flow injection spectrophotometry using gas-diffusion and an immobilized enzyme reactor, Am. J. Enol. Vitic. 50 (1999) 259. 

Wine analysis is also feasible with near-infrared spectroscopy. This f. - technique provides a relatively straightforward method of analysing ethanol in wine. The O—bond in ethanol produces a near-infrared mode that is easily distinguished from the O—mode of water. In the... 

Ethanol in wine is mainly produced by the alcoholic fermentation of sugar in must. However, grape cells are also capable of forming small quantities, mainly under anaerobic conditions (carbonic maceration see Volume 1, Section 12.9.3). The appearance of traces of ethanol in grapes results from alcohol dehydrogenase activity, which acts as a marker for ripeness. 

A number of FIA applications are made possible by the fluorimetric determination of nicotinamide adenine dinucleotide in its reduced form at 365 nm (excitation) and 400 nm (emission). This way ethanol in wine and pyruvate in milk can be determined. 

Some recent and convenient procedures have been used to determine both ethanol content and extract. Regarding ethanol, an AO AC-approved method exists for the determination of ethanol in wine based on GC and the technique is very precise and accurate. An increasingly popular technique is the use of near-infrared spectroscopy. Instruments are commercially available allowing the determination of ethanol and other common parameters in wine. 

Individual sugars can also be measured by separation techniques such as Hquid chromatography (LC) and capillary electrophoresis (CE). Separations are usually ion-exchange based with refractive index detection. With this type of method it is also possible to determine simultaneously other wine constituents such as carboxylic acids, sugars, glycerol, and ethanol in wines. Different detection modes may be used in conjunction with postcolumn derivatization or alternatively the eluate may be directly analyzed by ETIR. 

Stevens, D.F. and C.S. Ough. 1993. Ethyl carbamate formation reaction of urea and citrulline with ethanol in wine under low to normal temperature conditions. Am. f. Enol. Vitic. 44 309-312. 

H.p.l.c. on an H -form cation exchange resin with an acidic eluant was used to determine glucose and fructose, carboxylic acids, glycerol and ethanol in wine and grape musts. ... 

Acetic acid, CH3—COOH, is formed when the ethanol in wine and apple cider reacts with oxygen in the air. A solution of acetic acid and water is the vinegar used in food preparation and salad dressings. 

A carboxylic acid contains a carboxyl group, which is a hydroxyl group attached to a carbonyl group. Many carboxylic acids have common names, which are derived from their natural sources. Formic acid is injected under the skin from bee or red ant slings and other insect bites. Acetic acid is produced when ethanol in wines and apple cider reacts with the oxygen in the air. Propionic acid is obtained from the fats in dairy products. Butyric acid gives the foul odor to rancid butter (see Table 14.2). 

Several applications have been reported for food analysis, including the determination of ethanol in wines (Sramkova et al., 2014), trace inorganic mercury in mussel and tuna fish tissue (Mitani et al., 2014), phthalates (Clavijo et al., 2014), inorganic mercury (Mitani et al., 2014) in drinking waters, and the illegal food additive rhodamine B (Maya et al., 2012a). 

Sramkova, L, B. Florstkotte, P. Solich, and H. Sklenarova. 2014. Automated in-syringe single-drop head-space micro-extraction applied to the determination of ethanol in wine samples. Anal. Ghim. Acta 828 53-60. 

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