The Aging of Wine

The aging of wine, and its ability to potentially improve in quality, distinguishes wine from most other consumable goods. While wine is perishable and capable of deteriorating, complex chemical reactions involving a wine's sugars, acids and phenolic compounds (such as tannins) can alter the aroma, color, mouthfeel and taste of the wine in a way that may be more pleasing to the taster. The ability of a wine to age is influenced by many factors including grape variety, vintage, viticultural practices, wine region and winemaking style. The condition that the wine is kept in after bottling can also influence how well a wine ages and may require significant time and financial investment.

The ratio of sugars, acids and phenolics to water is a key determination of how well a wine can age. The less water in the grapes prior to harvest, the more likely the resulting wine will have some aging potential. Grape variety, climate, vintage and viticultural practice come into play here. Grape varieties with thicker skins, from a dry growing season where little irrigation was used and yields were kept low will have less water and a higher ratio of sugar, acids and phenolics. The process of making Eisweins, where water is removed from the grape during pressing as frozen ice crystals, has a similar effect of decreasing the amount of water and increasing aging potential.

In winemaking, the duration of maceration or skin contact will influence how much phenolic compounds are leached from skins into the wine. Pigmented tannins, anthocyanins, colloids, tannin-polysaccharides and tannin-proteins not only influence a wine's resulting color but also act as preservatives. During fermentation adjustment to a wine's acid levels can be made with wines with lower pH having more aging potential. Exposure to oak either during fermentation or after during barrel aging will introduce more phenolic compounds to the wines. Prior to bottling, excessive fining or filtering of the wine could strip the wine of some phenolic solids and may lessen a wine's ability to age.

The storage condition of the bottled wine will influence a wine's aging. Vibrations and heat fluctuations can hasten a wine's deterioration and cause adverse effect on the wines. In general, a wine has a greater potential to develop complexity and more aromatic bouquet if it is allowed to age slowly in a relatively cool environment. The lower the temperature, the more slowly a wine develops. On average, the rate of chemical reactions in wine double with each 18 °F (8 °C) increase in temperature. Wine expert Karen MacNeil, recommends keeping wine intended for aging in a cool area with a constant temperature around 55°F (13°C). Wine can be stored at temperatures as high as 69°F (20°C) without long term negative effect. Professor Cornelius Ough of the University of California, Davis believes that wine could be exposed to temperatures as high as 120 °F (49 °C) for a few hours and not be damaged. However, most experts believe that extreme temperature fluctuations (such as repeated transferring a wine from a warm room to a cool refrigerator) would be detrimental to the wine. The ultra-violet rays of direct sunlight should also be avoided because of the free radicals that can develop in the wine and result in oxidation.

Wines packaged in large format bottles, such as magnums and 3 liter Jeroboams, seem to age more slowly than wines packaged in regular 750 ml bottles or half bottles. This may be because of the greater proportion of oxygen exposed to the wine during the bottle process. The advent of alternative wine closures to cork, such as screw caps and synthetic corks have opened up recent discussions on the aging potential of wines sealed with these alternative closures. Currently there is no conclusive results and the topic is the subject of ongoing research.




Source : http://en.wikipedia.org/wiki/Aging_of_wine

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