Agriculture Reference
In-Depth Information
Port wines are fortified to an amount of alcohol around 20%
before the primary fermentation has completed. The high
level of alcohol from fortification stops the fermentation very
quickly so that high sugar levels remain.
Because distilled spirits are expensive (why would you use
the cheap stuff?), the financially practical batch size for
fortification will likely be limited to a gallon or so. Even
though fortification will stop the yeast fermentation, the wine
will continue to undergo small changes from aging for as long
as forty years.
The first step in fortification is to assess the level of alcohol in
the wine. For wines fermented to dryness, this is easy—you
can just use the potential alcohol corresponding to the original
hydrometer reading of the must. For wines that will retain
sweetness, you will take a hydrometer reading every day or
two during the primary fermentation and perform the
fortification at a point corresponding to the degree of
sweetness you want to retain. In general, you'll want to do
this at a reading between 1.010 for slightly sweet to 1.040 for
very sweet. The alcohol level level can be determined by
subtracting the potential alcohol at the point of fortification
from the potential alcohol at the start of fermentation.
For example, if the original specific gravity of my must was
1.093 (12.8% potential alcohol) and I perform my
fortification when the must reaches 1.027 (3.7% potential
alcohol), the level of alcohol is 12.8% - 3.7% or 9.1%.
Once you know how much alcohol the wine already contains,
you must decide how much alcohol you want it to contain
