In a small restaurant near my house hangs a sign that reads something along the lines of "To take wine into your mouth is to savor a droplet of the river of human history" (Clifton Fadiman, N. Y. Times, 8 Mar '87). As a group, we have been, according to the quote, anyway, been having a lot of history lessons, starting with the pitcher of wine we enjoyed at our first group dinner in Rome and continuing throughout the trip, with our most recent taste occurring on a fairly large vineyard in small town near Siena called Montalcino. There, we met with the owner of the vineyard and his wife, and he told us a bit about the winemaking process while showing us the barrels wine is aged and stored in. I was curious about what was really happening inside the barrels, so I did a bit of research recently, and I found that topics we learn in biology and chemistry classes are very applicable to the winemaking process.
Wine, obviously, begins with the grapes. As Enrico taught us the other day, different regions are better for different types of grapes. Reigons of France are great for growing Chardonnay, just as the Montalcino reigon is perfect for growing Sangiovese grapes, the type of grape that the winemaker we visited used for making Rossi and Brunello wines (http://www.winespectator.com/webfeature/show/id/Brunello-Under-Fire_4075). According to the winemaker, the grapes in his vineyard are picked by cutting them off of the trees with scissors, but machines are used by some other vineyards.
After the grapes are picked, they are crushed in ...you guessed it...a crusher (see photo below). The crusher is a machine that contains a perforated drum similar to a strainer inside, allowing for the grapes’ juice and skins, a mixture called the "must," to move on to the next step of winemaking, leaving the stems behind. Red grapes’ must is moved directly to the fermentation tanks, while white grapes’ must must be filtered to remove the skins from the mixture.
Fermentation,
the yeast-requiring process that makes the must alcoholic, occurs in
fermentation tanks: large, airtight, stainless steel barrels that are
kept at a constant temperature of four degrees Celsius. To begin the
fermentation process, the winemaker adds sugar and yeast, with the
yeast type and amount of sugar added depending on the type of grape(s)
being used.
As
you might remember from bio class, fermentation is an anaerobic
variation of the cellular respiration cycle, hence the use of tanks
that are airtight. It turns glucose, a sugar that is very readily found
in the must, into ATP, carbon dioxide, and ethanol (shown below), the
alcohol found in wine and other alcoholic beverages. Fermentation
begins with a process called glycolysis, which breaks down glucose into
two molecules of pyruvate (shown below). After glycolysis, each
molecule of pyruvate is turned into carbon dioxide and ethanol through
a complex biochemical process. The overall reaction for fermentation is
as follows, and the fermentation process takes two to four weeks:
C6H12O6 → 2 C2H5OH + 2 CO2
Pyruvate
Ethanol
After
fermentation, the alcoholic must mixture is filtered to remove the
yeast and, in the case of red wines, the grape skins. Next, the mixture
must be aged in oak barrels for anywhere from a few months to a few
years, depending on the quality desired of the wine (I see Meridith just posted about what goes on inside the barrel during this maturation period, so look at her post to read about that). After that, the
wine is finally ready to be bottled and sold to the thirsty.
Wine: the beverage rich in both science and history.
Main Source -
http://science.howstuffworks.com/innovation/edible-innovations/winemaking.htm
No comments:
Post a Comment