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California is home to thousands of
wineries, and the Department of Enology and Viticulture at the University
of California at Davis is recognized as the preeminent center for
the study of wines and winemaking. It is only natural that specific
glassware for the analysis of wine would be developed in California.
Volatile acids in wine include
acetic, formic, and butyric acids, and other fatty acids. Lactic,
succinic, sorbic acids are slightly steam-distillable, but are not
considered part of the volatile acids; their contributions must be
adjusted for. Carbon dioxide, from fermentation, and sulfurous acid,
from wines high in sulfur dioxide, also affect the total acidity and
can contribute to error.
High volatile acid content
in wine is an indication that bacteria, especially Acetobacter, which
spoil wine, are present; the wine may turn to vinegar. Some acetic
acid (i.e. vinegar) is acceptable in wine, somewhat more so in older
wines.
The government requires
that wine be tested for volatile acids; http://waterhouse.ucdavis.edu/winecomp/va.htm.
Federal, California and European regulations have differing standards; California's
are generally a little stricter.
The winemaker needs to know
the volatile acidity to meet legal limits, to track the acidity during
storage, as well as to watch for spoilage. He or she will typically
check the acidity several times during the production process.
Steam distillation of the volatile
acids requires that steam be bubbled through the sample of wine to
be tested. The volatile acids are vaporized and condensed in a Graham
condenser. The distillate is collected and titrated to determine the
total steam-distillable acidity.
See also notes about our
improvements, and a bit about the
history.
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