juice from both red and white wine grapes is without color.
In red wine production, the skins are fermented with
the crushed juice to give it color and flavor. Unless a
full-bodied white wine is desired, the skins and seeds are
usually removed from the must after only a few hours leaving
juice known as "free run." The skins are pressed to extract
all the remaining juice, called "press juice." The free
run and press juice are then filtered in preparation for
fermentation. At some point in production, the press juice
may be blended back into the free-run. Next, the juice is
placed in stainless steel tanks or oak barrels where the
wine will ferment following the addition of yeast. White
wine fermentation lasts from three days to three weeks.
fermentation has run its course, the vintner will stop the
process and filter the wine to remove solids and yeast remnants.
The wine is then aged for a period of one week to a year
in stainless steel, oak or redwood containers, or it can
be aged in the bottle. After aging, the wine may be blended
with other wines with different characteristics to create
the desired style. The next step is "finishing," a process
by which the wine is stabilized and filtered before bottling.
Substances such as egg whites or gelatin are added to remove
astringent substances or proteins, which can cloud the wine
and give off flavors. Sulfites may also be added to prevent
oxidation and bacterial spoilage.