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w i n e MAKIN G Figure III: Benefits of élevage BALANCE BODY COLOR WINE QUALITY FLAVOR STABILITY TASTE ent combinations: between tannins, between anthocyanins, and between tannins and anthocyanins together. The consequences of these chemical reactions are the following: •The color of the wine is stabilized and its intensity increases, • There is a decrease in the bitterness and astringency of the wine, and • Tannins are transformed to give the wine its softness. Mel_Knox_Dir11.qxp 12/13/10 c. Other exchanges through the membrane One must consider porosity to gas and permeability to liquid and gas. If it works one way for oxygen (from outside to inside the barrel), it can work the other way for components such as ethanol, water, and gas as carbon dioxide. Although there is an apparent loss, the wine becomes more concentrated — this phenomenon is called the "angels' share." 1:13 PM Page 1 Figure III: Benefits of élevage. Second function — The barrel is a membrane between wine and the cellar environment When we discuss the environment of a barrel, we refer to the cellar's humidity, average temperature, and ventilation. a. Oxygen Oxygen in the atmosphere will interact with wine in a barrel. The permeability and porosity of the barrel allow for several interactions: • Oxygen can enter the barrel between the bung and the staves and then dissolve in the wine. •Oxygen can travel through the wood of the barrel. • Oxygen can enter between the staves into the wine. Different steps in the winemaking process also allow oxygenation to occur. The following statistics are what we found in different sources in the technical literature. •During each racking, 6 mg/L of oxygen dissolves into the wine, • Each topping up of a barrel adds around 4 mg/L to the wine, and •Maturation itself — the transfer of oxygen when the wine remains in the cask — can represent 35 mg/L. In summary, a large amount of oxygen is brought to a wine during élevage in barrels, through the barrels themselves and during different steps of élevage (racking and topping up). b. Reactions allowed by this interaction with oxygen Barrels in the cellar are interacting with the environment. Oxygen crosses the limits of the barrel through different pathways, and is diluted into the wine. Oxygen allows ethanal to be produced in the wine. Both oak and wine polyphenols can interact with ethanal and generate differpr actica l win ery & vin eya r d JANUARY 20 14 37