Wine Spoilage
Even with modern winemaking, storage and
shipping technology about five percent of all
wines arrive at the table bad to some degree.
Here are some tips about how to spot them.
CORKING
It all begins with a cork... Even in this day of
high-technology plastics, many bottles are still
stoppered with an old-fashioned cork. A product
of the bark of a selected Mediterranean trees,
corks have many highly desirable and hard to
duplicated, attributes. Lightweight, resistant
to disease and airflow, flexible and attractive.
But cork, as a natural product, is subject to
attack by microorganisms. Certain species of
fungus, present anywhere wine is stored, can
infiltrate the cork producing a compound called TCA (1,2,4-trichloroanisole, for those
interested).
TCA and other factors produce in wine
unattractive odors and tastes, similar to wet
cardboard, mushrooms, mold and even unwashed
socks. Even if the odor is mild the taste may be
somewhat bitter and lack fruitiness.
COOKING
Moving wine from the vineyard to the home or
restaurant table involves trips of anywhere from
dozens to thousands of miles. Given that it's
surprising that only five percent of wine is
partially spoiled due to excessive temperatures.
High temperatures cause liquids like wine to
expand slightly, which increases the pressure
inside a corked bottle. This pressure can cause
the cork to get pushed slightly up. When the
wine cools down again, air seepage can occur.
If the temperature becomes high enough, the wine
can be literally cooked. If cooking has taken
place, the taste will be evident. The fruit
flavor will convey more stewed prune than fresh
berry. Look for corks that sit above the lip of
the bottle, or levels of liquid too far near the
base of the neck.
OXIDATION
Improper storage, such as excessive heat or cold
and incorrect humidity levels, can cause corks
to shrink or crack. Either of these will cause
infiltration of unwanted amounts of air into the
bottle, causing oxidation. Oxidation is what it
sounds like, oxygen, a volatile compound,
combining with a wide variety of wine components
and altering them.
Some amount of air, in small amounts over a
period of years, may be desirable to ensure
proper aging. But even well before producing
vinegar, it's possible to spoil a wine from
allowing too much air to reach the wine. Wine
which has become fruitless and resembles old
Madeira (deliberately produced in open air vats)
is almost certainly oxidized.
SULPHUR and SEDIMENTS
Sulphur is a common preservative in winemaking
which can help stabilize wine. But in excessive
concentrations it produces an undesirable aroma
and flavor. Its characteristic mothball or burnt
matches smell or taste makes it easy to spot.
Some sediment in wine is acceptable and normal.
Ports and older wines, even whites, often
accumulate material and properly poured or
decanted and served are fine. Tartrate crystals
too, for example, will naturally form in some
wines especially when chilled for shipping and
storage. They do no harm, but avoid pouring and
tasting them.
REFERMENTATION
In rare cases, it's possible for dormant yeasts
to remain in the wine and some amount of
additional fermentation to take place during the
years of shipping and storage. Champagne, for
example, is deliberately refermented in the
bottle. But for non-sparkling wines, this
effervescence is undesirable, but easily
spotted.
Techniques of manufacture, bottling, shipping,
and storage continue to improve and the odds of
encountering one of these conditions is rare. If
you find a wine that's distasteful, chances are
it simply isn't for you.