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winery sanitation products. If not controlled, TCA can contaminate not just
a single batch of corks (and thus wine) but an entire cellar, and once
entrenched it is very difficult to eradicate. As a result, most wineries have
eliminated the use of chlorine-based cleaning products. It is also less prevalent
now that many wines have Stelvin closures (screwcaps) or artificial
corks. Most natural wine corks come from Portugal, and in recent years
cork producers are bleaching the corks with peroxide instead of chlorine, as
well as steam-cleaning and using carbon dioxide washes, a technique developed
by the perfume industry to remove unwanted odours.
Nevertheless, it still occurs, and if your wine on first sniff and sip has lost
its fruit and has that mouldy undertone, then send it back. Most restaurants
will not argue and if they do, insist.
Some other nasty wine infections include:
• Volatile acidity (“VA”): This either gives the wine a vinegar
(acetic) or nail polish (ethyl acetate) aroma and taste and comes
from wild yeasts and bacteria such as acetobacter that infect the
wine if not properly protected in the winery. It is a particular problem
with late harvest wines and icewines.
• Hydrogen sulfide (“H2S”): This creates aromas of sour well gas or
rotten eggs (think of your last trip to a pulp mill town!). H2S is generally
thought to be a metabolic by-product of yeast fermentation
in nitrogen-limited environments, and the yeast ferments via the
sulfate reduction pathway. Fermenting wine is often supplemented
with diammonium phosphate (“DAP”) as a nitrogen source
to prevent H2S formation.
• Sulphur defects: This is a particularly nasty category including
mercaptans and dimethyl sulfide, where rotten garlic or onion permeate
the wine’s aromas. Other aromas can be canned corn, or
burnt rubber, or even pig manure! It is caused by a reaction of
hydrogen sulfide (“SO2”) used to preserve the wine with other
wine components such as ethanol (often from an overly long
period of lees contact) or from the breakdown of sulphur-containing
amino acids, especially in red wine.
• Brettanomyces: This one is quite controversial, as in some winemaking
areas in France or Italy, and more recently in California, a
certain level of “Brett” is believed to be a good thing that adds to a
wine’s complexity. The cause is infection of a wine (especially reds)
with the wild yeast called Brettanomyces or Dekkera that produces
an array of metabolites to grow in the wine, some of which are