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| Grape growing, winemaking and wine maturation |
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| Maturation |
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 Most types of wine undergo one type of aging or another. Different types of maturation have different purposes. One common form for both reds and whites is barrel maturation. This refers to aging in small oak casks of approximately 225 liters. These are known as barriques (Bordeaux barrels). The 228 Burgundy pièce is a slightly different shape, but serves essentially the same purpose (although the staves are thicker, and it is often bound with a chestnut hoop). Other barrel sizes are the 205-liter Champagne barrel and the 132 liter feuillette, formerly used in Chablis.
This type of aging can have three effects – a flavoring of the wine that comes from compounds in the wood, an improvement in clarity that comes from gradual settling of the wine, and a fixing of the phenolic compounds (polymerization) because of a slight and gradual exchange between the air outside the barrel and the wine. All of the effects become more pronounced the longer the wine is left in cask.
Sometimes wine is aged in larger barrels. Shapes include the tonneaux (900 lit), the demi-muid (600 lit) in Chateauneuf, and the various types of foudres, botte (in Italy), pipes (for Port), and butts (for Sherry), all of which vary in size. In the case of larger barrels, the ratio of surface to volume is much smaller, and the wine is correspondingly less marked by wood flavor. The other effects of barrel aging, however, still affect the wine.
 
Tank aging is also used. Tanks do not mark the wine in any way, but can be used as vessels for lees aging. By nature reductive (because stainless steel and concrete are not porous), oxygen can be excluded completely by blanketing with inert gas.
Some winemakers wish to introduce a certain amount of oxygen without racking, and one technique that is gaining increasing favor is micro-oxygenation. This is a system of injecting minute amounts of oxygen into red wine that is aging in tank, either slowly (over the course of weeks) or all at once. This is done to encourage the stabilization of the phenolic compounds without necessitating racking by hand. It is done at some wineries in such a way as to mimic racking. In this case is used as a labor saving device.
Since it causes tannins to bind with anthocyanins, in higher doses it can make a wine very soft and velvety in texture. It is known for imparting a characteristic “chocolatey” character to the tannins. This effect can be overdone, however, turning the wine into a caricature.
Bottle aging is also sometimes used, and in some cases required by law. This type of aging produces different results because there is no polymerization of the polyphenols. There is, however, added complexity because of the formation of esters. Esters are compounds formed by the combination of acids and alcohols. They are volatile, and thus contribute to the formation of the bouquet.
Some Old World regions require minimum aging periods for their wines. The most famous example of this is the minimum aging period established for Champagne, as outlined in the chapter on Champagne.
In Italy, Riserva Chianti must be aged for two years and three months in bottle (i.e. release the third January 1st from the harvest), although the minimum bottle aging period is due to be dropped, however. Brunello must spend four years from the January following the harvest, while Riserva must spend five. Of this time, two years must be barrel aging. Barolo must be aged for three years, and Riserva for 4 _ years, with one year minimum in wood. Barbaresco must be aged 21 months total with a minimum of 9 months in wood, and Riserva must be aged 45 months.
In Spain, the laws of all regions have been changed to ensure the same minimum aging requirements for each. Vino Joven is aged less than Crianza, which must be aged two year total and at least 6 months in oak for reds and one year total, half of that in oak for white and rosé crianzas. Riservas must have three years minimum aging, with at least one year in oak (two years total with 6 months in oak for whites and rosés), and Gran reserves must be aged two years in oak and three years in bottle for reds, and four years total with 6 months minimum in oak for rosés and whites.
Another example of minimum aging requirements is for Muscadet sur lie. This wine (which derives much of its character from the lees aging) must be aged at least through the winter and be bottled directly off the lees from the beginning of March through the end of June (when 80% of the wines are bottled), or from the 15th of October through the end of November. The wine may be sold only from the third Thursday in the March following the harvest. The shortest minimum aging is probably Beaujolais Nouveau, which cannot be released before the third Thursday in the November following the harvest.
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Wine Regions of the World
