Oxygen

Oxygen
has always been a blessing and curse as it reacts to the
world around it. From way back in grade school science we
have been taught that oxygen is the core of the building
blocks of life. Animals need it to breathe, fire to burn,
without it life as we know it would not exist. On the flip
side, oxygen is a main element in degradation and ageing –
it is continuously combining with life’s molecules and
slowly destroying them, the result being oxidation. For
wine, oxygen has a complex relationship starting in the
vineyards all the way to post-bottling.

Old styles of winemaking
are aerobic, meaning that the preventative methods of making
sure oxidation was occurring were unknown or disregarded.
Oxygen would be picked up during pressing, traveling from
fermentation to barrel, during the clarifying process and
during bottling. Because of this the fruit flavors would be
diminished and the finished wine would be lacking in these
notes. This is not to say that aerobic winemaking is always
bad – for certain styles of sherry, vin jaune and tokaji it
is part of the character of the wine. And it must be noted
the oxidation is being monitored and kept under
control.

Modern wine making is made
via anaerobic methods, without oxygen, or at least under
very controlled situations. To prevent oxygen from reaching
wine today is not that difficult, it just needs good
discipline in all aspects of the winemaking process.
Interestingly, because of modern methods such as stainless
steel tanks, some of the sulphur dioxide becomes reduced to
hydrogen sulphide, giving the wine what is known as a
reductive taint. For some this is a “dirty” smell. But
oxygen is not the culprit in these cases. Starting after
picking, the grapes are sprayed with antioxidant powder
called potassium metabisulphite. This white powder is stable
when dry, but removes sulphur dioxide when wet, which
protects the juice during accidental breaking of the skins
or after the pressing occurs.

Other modern techniques use
oxygen in a beneficial method, some of which seem a little
ironic, such as hyperoxidation. A common and correct belief
is that wine needs to be protected from oxygen after
fermentation – though some winemakers believe if the wine is
protected too much, it is even more susceptible to
oxidation. Ironically, if the must is allowed some contact
of oxygen before fermentation, it destroys some of the more
susceptible components of the juice and will result in a
finished wine that is more stable. Hyperoxidation, with its
use of oxygen at the correct time, still yields the fresh
vibrant fruit that is typical of modern
winemaking.

Another form of tempered
oxygen use is micro-oxygenation. Unlike hyperoxidation, this
technique is used with fully fermented wine. This is a
fairly new technique that many modern winemakers have
adopted. The principle is that of the slow oxidation that
barrels use is applied when the wine is in tank. An
extremely small amount of oxygen bubbles are added (so small
that you can’t see them) which results in a wine that is
smoother and softer, with better integration of tannins.
Michael Rolland is a big proponent of this
technique.

Even after bottling, the
process of oxidation continues (now that it has been proven
corks are porous), allowing an extremely small amount of air
in. Assuming a correct cork and seal, another factor in the
rate of oxidation is the size of the bottle. The logic is
cork will give the same amount of oxygen from (more or less)
each bottle to bottle. As this is hopefully the only way
oxygen gets in, it stands to reason a magnum will see less
oxygen than a bottle, and a bottle less than a half bottle,
in relationship to total wine volume.

One of the questions I am
consistently asked in my classes is: “What’s the best way to
preserve the quality of an opened bottle until the next day
or days?” Well, the best way is to finish the bottle;
outside of that, in my experience, has been the use of inert
gases, which for preservation units of a bottle here or
there is nitrogen or argon. They can be very reasonable,
about $15 a can retail. By spraying either of these gases
into the bottle and then restopping with the cork, the gas
rests on top of the wine preventing any further oxygen from
entering the wine. Naturally there is oxygen still in the
wine already because the wine has been poured, however, the
process of oxidation is slowed considerably in comparison to
just sticking the cork back in. The more expensive systems,
some of which are installed in wine retail stores in the
Boston area, do the same with even more control. This is a
great way for retail clients to sample the wine before they
buy at their convenience, not when the store has a wine
tasting.

Oxygen is still a blessing
and curse, but as time and technology proceed, its benefits
are continually increased while its deficits, though
damaging, are becoming less and less of an issue.