Many wines
improve in quality during barrel and bottle storage. Such wines eventually reach their
peak and with further aging begin to decline. During the aging period, acidity decreases,
additional clarification and stabilization occur as undesirable substances are
precipitated, and the various components of the wine form complex compounds affecting
flavour and aroma.
Wines are usually aged in wooden containers made of oak, allowing oxygen to enter and
water and alcohol to escape. Extracts from the wood contribute to flavour. Humidity
affects the kind of constituents that escape, with alcohol becoming more concentrated in
wine stored under conditions of low humidity and weakening with high humidity. As the
water and alcohol are released, volume decreases, leaving headspace, or ullage, that is
made up by the addition of more of the same wine from another container.
Some red table wines appreciate in quality, developing less astringency and colour, and
a greater complexity of flavour with aging in oak cooperage of up to 500-gallon size for
two to three years. In the best red wines, additional improvement may continue with two to
20 years of bottle aging (the rate of aging being lower in the bottle than in the barrel).
Many dessert wines improve during cask aging, particularly sweet sherries, but extraction
of excessive wood flavour must be avoided. Those rosé and dry red wines that will not
improve with long cask and bottle aging are aged for a short period of time, clarified,
and then bottled. More than 90 percent of all table wines are probably marketed and
consumed before they are two years old. In dry white wines, a fresher flavour is
considered desirable, and the chief benefit of aging is greater clarification as various
undesirable substances are precipitated. These wines are rarely aged in the wood for long
periods, and some are never kept in wood. This change is possible because of the
efficiency of new clarification methods. Earlier bottling of white wines reduces costs for
storage and for handling in wooden cooperage and produces fresher, fruitier flavour. Sweet
white table wines profit by some aging in wood.
