Table wines, acidic components

As with other flavor and odor-active compounds in wine, detection and interpretation (either positive or negative) depend on the matrix in which those components are present. In the case of acetic acid, aroma thresholds (in wine) have been reported to be as low as 100-125 mg/L (Riesen, 1992). The concentration at which the acid is regarded as detrimental is considerably higher, ranging from >700 mg/L (Zoecklein et al., 1995) to 1200-1300 mg/L reported by Margalith (1981). The latter two levels are at, or exceed, legal maxima as established for table wines by both OlV and BATF (see Table 2-3). 

Table X illustrates the successful application of formaldehyde precipitation as a means of estimating the flavonoid and nonflavonoid contents in a mixture. The mixture consisted of catechin as the flavonoid and caffeic, vanillic, and syringic acids as the nonflavonoids. The catechin was 86% precipitated (lower than usual because of the low level), but the other substances were not significantly precipitated. The slight apparent loss of caffeic acid is attributable to experimental variation since in many other experiments the lack of reaction and precipitation or co-precipitation of caffeic acid or chlorgenic acid has been demonstrated. Allowing for the same slight solubility of the catechin-formalde-hyde product in the mixtures as in the single component solution, the analysis of the mixtures gave 95.7-107.6% of the calculated value. This indicates no significant co-precipitation or entrainment of the nonflavonoids as the flavonoid was removed. This result has been verified a number of times with different substances added to model solutions and wines (21, 22).

Analytical determination of peptides in wine requires sample preparation, involving their isolation from the remaining components, mainly high molecular weight nitrogen compounds, free amino acids and phenols. Table 6B.1 summarizes the procedures used in the literature for the extraction of wine peptides before their analysis by different analytical techniques and with different detection systems. 

As an example, Tables 13.14 and 13.15 show the results of applying principal components analysis to the 10 volatile compounds (methanol, 1-propanol, isobutanol, 2-and 3-methyl-1-butanol, 1-hexanol, cw-3-hexen-l-ol, hexanoic acid, octanoic acid, decanoic acid and ethyl octanoate) analyzed in 16 varietal wines (Pozo-Bay6n et al. 2001), obtained with the STATISTICA program Factor Analysis procedure in Multivariate Exploratory Techniques module, and using Principal Components as Extraction method). The results include the factor loadings matrix for the two first principal components selected q = 2), which explains 70.1% of the total variance (Table 13.14). The first principal component is strongly correlated with d.y-3-hexen-l-ol (-0.888), 1-hexanol (-0.885), 1-propanol (0.870), and... 

Analysis of Phenolic Compounds. A Hewlett-Packard (Palo Alto, CA) Model 1090 HPLC System, was used to determine the levels of specific phenolic components. The HPLC system was equipped with a ternary solvent delivery system, a diode array UV-VIS detector, and HP ChemStation software for data collection and analysis. Full chromatographic traces were collected at 280, 520, 316, and 365 nm, and spectra were collected on peaks. The stationary phase was a Hewlett-Packard LiChrosphere C-18 coliram, 4mm X 250 mm, with 5 pM particle size packing. Operating conditions include an oven temperature of 40 C, injection volume of 25 pL, and flow rate of 0.5 mL/minute. The mefriod was based on a previously published method for phenolic components in wine (30) and used the modified solvent gradient shown in Table II. Solvent A was 50 mM dihydrogen ammonium phosphate, adjusted to pH 2.6 with orthophosphoric acid. Solvent... 

This series is shown in Table 2.4. The most important of these compounds is acetic acid, the essential component of volatile acidity. Its concentration, limited by legislation, indicates the extent of bacterial (lactic or acetic) activity and the resulting spoilage of the wine. As yeast forms a little acetic acid, there is some volatile acidity in all wines. Other C3 (propionic acid) and C4 acids (butyric acids) are also associated with bacterial spoilage. 

Table 2.4. Fatty acids in the aliphatic series among the volatile components in wine (Ribdrean-Gayon et al., 1982)...

After 8 hours of heating, anthocyanin solutions contain benzoic and cinnamic acids, dihy-droflavonols, catechins and a certain number of unidentified molecules. Furthermore, malvidin, the major component of wine coloring matter, has been found to be much more sensitive to thermal degradation than cyanidin (Table 6.4). The temperature factor should, therefore, be taken into account when wines are aging in barrels, vats or bottles, in order to protect their color. 

Ellagotannins occur as components of commercial tannic acid, various extracts and infusions (e.g. teas from medicinal herbs and bark of trees) and are also natural constituents of some alcoholic beverages matured in oak barrels, for example high quality wines and spirits, such as cognac, brandy, whisky, bourbon and rum. All components extracted from the wood are then degraded to some extent, which gives rise to various phenohc compounds that have a role to play in the flavour-active components of the alcohohc beverage (Table 8.44). 

Table 12.19 compares free run and press juice composition for traditional (crushed grapes) and carbonic maceration winemaking. In carbonic maceration press wines, the alcohol content is higher (caused by ethanol fixation) and the acidity lower (due to malic acid degradation). These wines also have lower concentration of phenolic componnds and other extracted components their dissolntion is diminished. 

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