Wines volatile acidity

Wine contains a mixture of straight chain fatty acids, usually referred to as short chain (C2-C4), medium chain (Ce-Cio), long chain (C12-C18), and a group of branched-chain fatty acids that include 2-methyl propanoic, 2-methyl butanoic, and 3-methyl butanoic acids. Acetic acid is quantitatively and sensorially the most important volatile fatty acid produced during alcoholic fermentation. Accounting for more that 90% of the total wine volatile acidity, acetic acid plays the most important... 

New enological technologies aim to lower volatile acidity, enhance sugar content in must in cool climates and vice versa reduce the alcohol content of wines from hot climates, modify pH, cations, anions and acidity to achieve tartrate stability, complement traditional ageing in oak barrels with the use of small oak wood particles and most recently, extract phenolic compounds by a countercurrent chromatography process from wine to diminish or enrich tannins in red wines. 

International limits for contaminants (4) are arsenic 0.2 mg/liter, volatile acidity 20 meq/liter for 10 vol % ethanol and 1 meq more for each per cent alcohol above 10%, lead 0.6 mg/liter, boron 80 mg/liter (as boric acid), bromine (total) 1 mg/liter (may be higher for wines from grapes of certain areas), bromine (organic) 0.0, fluorine 5 mg/liter, malvidin diglucoside 15 mg/liter, sodium 60 mg/liter (may be higher for wines from grapes of certain areas), and sulfate 1.5 grams/liter (as potassium sulfate). 

Volatile Acidity. Acetic acid is the primary acid formed during wine spoilage. Legal limits for it exist in all wine-producing countries, varying from 0.10 to 0.25% exclusive of sulfur dioxide and sorbic acid. The United States and California State limits are among the lowest. Good... 

It is probable that GLC determination of acetic acid, as distinguished from other volatile acids (propionic, lactic, etc.), will be used more often. A specific enzymatic procedure for acetate (35) reveals that only about two-thirds of the volatile acidity is acetic acid. However, the volatile acidity of commercial wines in modem wineries is usually well below the legal limits. 

The Taberie formula is usually used dr = dw — da + 1.000 where dr is the density of the residual, is that of the wine (less the volatile acidity and sulfur dioxide), and da that of the alcohol (both at 20°C). Tables for converting dr to grams of extract per 100 ml are available, but the proper table to use is the Plato sucrose table, not the Ackermann empirical table (66). 

Acetic acid content is used as a criterion for aerobic bacterial spoilage in wines. We can easily analyze two wines and determine that one has a lower volatile acidity than the other. But by every available standard of product quality judgment, the wine with the higher level of acetic acid may be the superior product. It is no accident that Subpart ZZ, Part 240, Title 26 of the Code of Federal Regulations allows the direct addition of acetic acid to correct natural deficiencies in grape wine. As sanitation practices have improved, the so-called natural acetic acid content diminished, and this has been correlated with lower consumer acceptance in certain cases (2). 

Acid formation Species of Brettanomyces, Hansenula, Pic Ilia, Saccharomyces As a contaminant in wines. Brettanomyces spp. Forms a higher concentration of volatile acids (also isobutyiic and isovaleric acids) than S. cerevisiae. Pichia species and other yeasts are responsible for acetic acid production in brines of domestic green olives not lactobacilli, as assumed for years (Vaughn et al., 1976). 

These components are alcohol, glycerine, sugars, colouring matters, albuminoid and tannin substances, inorganic salts (phosphates, sulphates and chlorides of potassium, sodium, magnesium, calcium and aluminium), non-volatile organic acids (especially tartaric, malic, succinic and lactic, partly free and partly combined as salts), volatile acids (especially acetic) and esters, the latter being the source of the particular perfume or bouquet of the wine. 

With an acid wine, it is well to prevent distillation of the volatile acids by neutralising the acidity with magnesium oxide or a few drops of concentrated caustic soda solution. Frothing is prevented by leaving the wine slightly add or by addition of tannin. 

Volatile Acidity.—This is determined by distilling the wine in a current of steam and estimating the acidity of the distillate as follows ... 

The volatile acidity is expressed as grams of acetic acid per litre, the number of c.c. of N/10-alkali being multiplied by 0-120 (or 0-240) if 50 (or 25) c.c. of the wine were taken. 

To apply this rule, the alcoholic strength (by volume) and the fixed acidity of the wine are determined. The latter, expressed as sulphuric acid, is increased by 07 (this corresponding with the maximum value of the volatile acidity in ordinary normal wines), and the value thus obtained divided by the alcoholic strength the quotient is the ratio sought. 

This rule is applied as follows To the total amount of alcohol1 in 100 c.c. of the wine are added the fixed acidity per litre expressed as sulphuric acid and One-tenth Of the volatile acidity, also as sulphuric acid per litre. 

EXAMPLES (x) An ordinary dry wine had an alcoholic strength xo, while total acidity plus one-tenth of the volatile acidity per litre (as sulphuric acid) is 4 20. Since 10 + 4 20 = 14 20, which exceeds 12 5, the wine is regarded as normal. 

Total acidity. This acidity, expressed as tartaric acid, varies from 4-5 to 15-X6 grams per litre. Wines rich in alcohol are relatively less acid than those of low alcohol content, owing to precipitation of the potassium bitartrate by the alcohol. Further, the total acidity of a wine diminishes as the wine ages, in consequence of precipitation Of this salt and also Of the tannin and likewise of decomposition of the malic acid into lactic acid Of one-half the equivalent acidity. On the other hand, the total acidity may be increased indirectly as a result of certain diseases of the wine which increase the volatile acidity. 

Volatile acidity. In ordinary red wines this acidity is, on the average, 0-4— 0 8 gram per litre, expressed as acetic add, and in white wines is somewhat less. In some wines, rich in alcohol and extract, such as " vins de conpage," it may surpass the above limits without producing an acetous character. In any case, however, if the volatile acidity exceeds 2 grams per litre, the wine is unsuitable for consumption. 

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). 

Later, other data on Vin Santo composition were also published by Bucelli et al. (1998) and Stella et al. (1998), who focussed their attention on the Tuscany production of Vin Santo, although they did not consider the occhio di pernice ones (Table 3.6). Here, it can be seen that with respect to the compositions considered previously, these here show less variability across all of the parameters. Moreover, the maximum alcohol content from 21% drops to 18.5%, while the volatile acidity is quite low, despite the high alcohol levels and the oxidative conditions in which these wines evolve respect to normal vinifications. The net extract instead decreases, especially in the maximum values. 

Accordingly, Muratore et al. (2007) used a S. uvarum strain for the fermentation of Malvasia delle Lipari, a grape variety that is also used for the production of sweet wine, and they investigated further the chemical and sensory properties of the relevant wines, comparing the results with those obtained with a commercial strain of S. cerevisiae. Lower volatile acidity, lower alcohol content, and higher total acidity were reported for the wine produced by S. uvarum, with higher scores for positive attributes assigned by a panel for the wine fermented with S. uvarum. 

Muratore, G., Nicolosi Asmundo, C., Lanza, C. M., Caggia, C., Licciardello, F., and Restuccia, C. (2007). Influence of Saccharomyces uvarum on volatile acidity, aromatic and sensory profile of Malvasia delle Lipari wine. Food Technol. Biotechnol. 45,101-106. 

Wine type Specific gravity (g/cm3) Sugar-free extract (g/l) Reducing sugar (g/i) Alcohol (%, v/v) Total acidity (g/l) Glycerol (g/l) Gluconic acid (g/l) Volatile acidity (g/l) pH Reference... 

Lafon-Lafourcade, S., Lucmaret, V., Joyeux, A., and Ribereau-Gayon, P. (1981). Use of mixed cultures for production of noble rot wines with reduced volatile acidity. C. R. Seances Acad. Agric. Fr. 67, 616-622. 

As already stated, the ameliorative effect of malo-lactic fermentation is equally important in the preparation of red wines—probably more so since a degree of tartrate not desirable in a red wine is often wanted in a white wine. It is also necessary to achieve bacterial stability. So long as malic acid remains in the wine and there is any presence of lactic bacteria, there is a risk, however remote, of delayed fermentation in the bottle accompanied by hazes and gassiness. In former times, French Burgundies often were subject to this accident. Finally, the slight increase of volatile acidity that accompanies malo-lactic fermentation may help to heighten and improve aroma and flavor. 

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