Biology Reference
In-Depth Information
barrels but also from chips, staves and even crude extracts (Barrera-
García
et al.
, 2007, Del Álamo Sanza
et al.
, 2004, Del Álamo Sanza and
Domínguez, 2006, Frangipane
et al.
, 2007).
9.3.4 Effect of oxygenation on flavano-ellagitannins - The
mongolicain story
9.3.4.1
Oxygen in wines - A few facts
Oxygenation is one of the crucial factors underlying the expression and
evolution of the organoleptic properties of wine such as astringency,
bitterness and color. Besides the aforementioned production of ethanal
from ethanol, numerous oxidations and subsequent transformations of
wine components take place upon aeration. The question of whether such
transformations improve or alter the quality of wine remains a matter of
much concern for enologists and wine scientists, but it is generally
accepted that a fast and excessive oxygenation has rather deleterious
effects, whereas a slow and continuous aeration can have a positive
impact on the organoleptic profile of wine (Ribéreau-Gayon
et al.
, 1983,
Pontallier, 1992, Moutounet and Mazauric, 2001). In this context, the
traditional aging of wine in oak barrels offers an adequate means to
temper its aeration by allowing a slow penetration of oxygen through the
wood (
ca
. 30-40 mg per year when using new barrels, Pontallier, 1992).
Although the quantity of detectable oxygen dissolved in wines at rest
during the one- to two-year period of this maturation process is low (
i.e.
,
20 to 50 μg/L, Moutounet and Mazauric, 2001), which is much lower
than the maximum solubility of oxygen in air-saturated wines at ambient
temperature and atmospheric pressure (
ca
. 8-9 mg/L), the capacity of
wines, especially heavy red wines, to absorb oxygen is very high, and
can reach up to 800 mg/L (Singleton, 1987, Moutounet and Mazauric,
2001). Once dissolved in wine, oxygen is thus progressively and rather
rapidly consumed by various substrates. Phenols and polyphenols are
unarguably among the first substrates in line to suffer directly or
indirectly from oxygen-mediated oxidation reactions leading to coupling,
condensation, polymerization and various other types of chemical (and
