On Food and Cooking

The substances important to wine quality
are not evenly distributed in the grape. The
stems contain bitter-tasting resins and are
usually separated from the grapes as they are
crushed. The skin holds much of the fruit’s
phenolic compounds, both pigments and
tannins, as well as most of the acid and the
many compounds that give the grape its
characteristic aroma. Like the stem, the seeds
at the center are full of tannins, oils, and
resins, and care is taken not to break them
open during the pressing.
As a mass of grapes is crushed in a
mechanical press, the first juice to come out,
the free run, is primarily from the middle of
the pulp, and is the clearest, purest essence of
the grape, sweet and largely tannin free. As
mechanical pressure is applied, juices from
just under the skin and around the seeds
augment the free run with a more complex
character. The extent of pressing will have an
important influence on the character of the