Concentration in red wine

Several Ci 3-norisoprenoids, including p-damascenone, p-ionone, and 1,1,6-trimethyl-1,2-dihydronaphtalene (TON), are powerful odorant in wine. P-Damascenone, which can be present in young wine at up to 180 times its odour threshold of 0.05 (Jig/L, has a stewed apple, rose, honey aroma (Francis and Newton 2005). P-Ionone, which has violet, flower, and raspberry aroma, is typically present at higher concentration in red wines. TDN develops a kerosene-like odour in aged whites, particularly Riesling (Francis and Newton 2005). 

Condensed tannins, especially procyanidins and catechins, present in aU of the solid parts of grape bunches (skin, seeds, stalk), are dissolved in the wine when it is left on the skins. Concentrations in red wine vary according to grape variety and, to an even greater extent, winemaking methods. Values are between 1 and 4 g/1. In dry white wine, the quality of settling determines the tannin... 

For many years, it was assumed that the low vinyl-phenol concentrations in red wines were due to the fact that, after their formation by yeast, they were converted into the corresponding ethyl-phenols by lactobacilli during malolacdc fermentation (Dubois, 1983). This interpretation is no longer accepted (Section 8.4.4). Indeed, it is now known that lactic bacteria are not involved in the prodnction of ethyl-phenols or vinyl-phenols in red wines. 

Ugarte, P., E. Agosin, E. Bordeu, and J.I. Villalobos. 2005. Reduction of 4-ethylphenol and 4-ethylguaiacol concentration in red wines using reverse osmosis and adsorption. Am.J. Enol. Vitic. 56 30-36. 

The complexity of wine composition is a central reason for the vast variety of wines in the marketplace. In addition to water and ethanol, the major components, a variety of organic acids as well as metal ions from minerals in the skin of the grape are present. Initially, all of these substances remain dissolved in the bottled grape juice. As the fermentation process occurs, the increasing alcohol concentration in the wine alters the solubility of particular combinations of acid and metal ions. Unable to remain in solution, the insoluble substances settle as crystals. Since the process of red-wine making involves extended contact of the grape juice with the skins of the grapes (where the minerals are concentrated), wine crystals are more common in red wines than in white wines. 

The amounts of analytes are compiled in Table 2.74. The results indicated that the concentration of polyphenols in red wines depends on both the grape variety and on the exogenous factors. The validation parameters of the method were good, the recoveries were in each case over 98 per cent, the coefficients of variation were between 1.3 per cent and 4.3 per cent, and the limit of detection ranged from 10/rg/l to 0.1mg/l. It was stated that the method is suitable for the determination of silbene compounds and quercetin in red wines [194],... 

In barrel-aged red, white, and model wines, naturally occurring furfuryl alcohol decreased in concentration with time. In red wine, furfuryl ethyl ether was identified as a degradation product after 55 wk of storage. The average percentage decrease of furfuryl alcohol was 73% (Spillman et al, 1998). 

Phenolic and antioxidant substances have usually studied in red wines, however, recently, interest has increased in the study of bioactive phenolics in white wines Frega et al. [374] isolated and measured concentration of ethyl caffeoate in Verdicchio white wine by HPLC-tandem-mass spectrometry (HPLC-ESI-MS/MS) and they also determined its effects on hepatic stellate cells and intracellular peroxidation. The resnlts were interesting in the light of other studies demonstrating the relationship between reactive oxygen species, chronic liver injury, and hepatic fibrosis. 

As a result of these condensation processes, concentrations of meth-oxy-containing malvidin anthocyanins decline more quickly in red wines than hydroxycinnamic acids such as caffeic acid with easily oxidizable catechol groups (De Beer et ah, 2008). This is particularly the case when higher levels of SO2 are maintained (Tao et ah, 2007), an observation that can also be linked to the ability of free SO2 to readily regenerate the original caffeic acid form (Makhofkina and Kilmartin, 2009). 

The anti-carcinogenic effects of resveratrol were also tested in vivo, by examination of mammary glands of mice treated with DMBA and TPA. A dose-dependent reduction in the formation of tumors was observed when the mice were treated with resveratrol. Resveratrol is present in high concentrations in the skins of grapes (50-100 pg/g) and, consequently, in red wine (1.5-3 mg/1). Based on these experiments, the consumption of grapes and grape products appears to have beneficial effects. 

Lead has been also determined in wine, other beverages, and fruit slurries by a simple and rapid FIA-HG-AAS method based on the generation of PbH4 in an HN03-H202 medium [65], Lead was analyzed directly in wine samples without mineralization or preconcentration, and results were compared with those obtained by ET-AAS. The employed coupling enabled these authors to reach a characteristic mass of 0.8 ng Pb from 100 p,L injections. Lead concentrations of 59 + 1 ig L1 (FIA-HG-AAS) and 58 + 1 p,g 1 1 (ET-AAS) were reported in red wine. 

Michel, J. Jourdes, M. Silva M.A. Giordanengo, T. Mourey N. Teissedre, P.L. 2011. Impact of concentration of ellagitannins in oak wood on their levels and organoleptic influence in red wine. J. Agric. Food Chem. 59 5677-5683. 

Garde-Cerdan, X, Xorrea-Goni, D., Ancm-Azpilicueta, C. (2002). Changes in the concentration of volatile oak compounds and esters in red wine stored for 18 months in re-used French oak barrels. Aust. J. Grape Wine Res., 8, 140-145. 

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