If you remember the song you're probably old enough to have a
glass. So much mystique about such an old beverage, you'd think
that everybody knows everything about it. After all it's been
around for thousands of years. Truth of the matter is there are so
many different versions out there and more being added every year,
it's impossible to know everything.
To start with: It's fermented red grape juice, though the juice
itself is greenish to colorless and only the skin of the grapes
adds the color in a process called 'maceration'. That is the big
difference between red and white wine.
Whereas white grapes sometimes skip the crushing and de-stemming
step in the wine making process and go straight to the press,
crushing is obligatory for red grapes as the pressing comes later.
The juice needs to be freed from the berries so yeast can do its
work and begin fermentation. Unbroken grapes will not ferment
normally. Red grapes are also de-stemmed at this point, but in many
cases stems are added back for increased tannins.
The biggest difference between red and white wine in terms of the
winemaking process is the 'maceration' to extract color, tannins,
and flavors ('phenolics') from the skin of the grapes. As the skins
soak in the juice, more and more of the red and blue pigments leach
out of skins into the darkening juice. This maceration process can
run from a few days to a few weeks, beginning at or before
fermentation and potentially well after.
The length of it is the winemaker's decision based on the style of
wine he or she wants to make, as well as grape variety. The longer
the maceration takes place, the higher the 'extraction' will show,
with wines that are deeply colored, highly tannic, and bursting
with flavors, but then they usually need time in the bottle to
settle down and mature. Shorter maceration time will yield softer,
more accessible wines that are often ready to drink shortly after
Different grape varieties have different amounts of tannins and
phenolics. Cabernet Sauvignon or Syrah for example have a lot of
color and extract, while others, such as Pinot Noir, have
relatively little and require more maceration to gain sufficient
color. This might explain how Champagne is 'white', but made from
red grapes. If the winemaker decides to begin maceration before
fermentation, the must is chilled to keep it from starting to
ferment. This is often referred to as 'cold soak.'
Red wine fermentation typically happens at higher temperatures than
for whites, as the light floral and fruit aromas emphasized by a
cool fermentation are less important to red wines. The warmer the
fermentation temperature, the more phenolics are extracted, which
makes the wine more robust and drier, as the higher temperature
converts more of the fruit sugar into alcohol.
With so many choices for a winemaker, not wonder there are so many
different wine flavors out there, and that not even figuring in the
characteristics of the grapes and the places they grow in.