Julien's Journal November 2015 (Volume 40, Number 11) | Page 47
by John B. Donovan
John is always up for a glass of wine, especially when shared with friends. While
his first choice is usually big reds, he’s
been known to enjoy dry crisp whites as
well. He is also known to enjoy good craft
beer on a fairly regular basis. He is the
executive director for the Dubuque Mercy
Health Foundation.
H
ave you wondered how wine
– fermented grape juice – can
sometimes smell like tobacco
or vanilla, and taste like cherry
pie or leather? If so, you are experiencing stereoisomers. Now, I am hardly
the person to explain chemistry to anyone,
but suffice it to say that stereoisomers
are different configurations of the same
chemical compound. For example, scents
common to California Chardonnays are
apple and butter. You have all tasted the
big, buttery-ness of an oaken Chardonnay.
But, the winemaker has not added any butter or even a dash of apple. Except in fruit
wines such as strawberry or cherry wine,
wine is made solely from grapes.
main fruit acids: tartaric, malic, and citric
in approximately a 3:2:1 ratio respectively.
These components, as in all fruits, provide
tartness. Tartaric is predominant in grapes,
malic is an apple acid, and citric is citrus
acid. The combination of these three acids
can create many interesting wine flavors
and can mimic other kinds of fruit. Further,
many wines go through a second fermentation where microbes convert most or all of
the malic acid to lactic acid. Lactic acid is
the same component that gives yogurt its
tartness, and can add buttery notes to a
wine’s flavor.
Esters, a compound produced by the reaction between an acid and an alcohol, are
the aromatic, fruity compounds in wine,
formed during fermentation, malolactic
fermentation (MLF), and aging. They can
come from the grape, but most are produced by yeast during fermentation and
aging. Esters make a wine smell fruity.
Esters degrade in whites over time, but can
increase in red wines. Young wines are full
of esters, especially new whites during the
first year after fermentation. Reds, though,
are seldom released until after the new
wine esters have disappeared. More stable
esters are responsible for bringing back the
fruity complexity that we refer to as bottle
bouquet and is a major reason proper aging
improves red wine.
Acetic acid, more commonly known as
vinegar, is present in all wines to some
degree. In these small amounts it provides
complexity and finish. Too much, of course,
the wine can taste like it should be used to
dress a salad. Again, proper storage will alleviate this risk.
Pyrazines are compounds that offer notes
of grass or bell pepper in Cabernet Sauvignon, Cabernet Franc, Merlot, and Sauvignon Blanc. They come from the fruit
itself and often indicate that the grapes
were harvested unripe or the crop was not
exposed to enough sunlight.
The Growing Climate
It’s no secret that climate affects every
vintage, every year, but it also plays a
critical role in the development of the individual grape clusters and their intrinsic
flavor profiles. For example, a wine’s taste
and mouthfeel will be completely different
depending on where it was grown. Take
a Cabernet Sauvignon grown in a cooler
region and one grown in a warm, sunny
setting. What happens to the grapes? In
the cooler areas, the Cabernet grapes will
often display tart, tight flavors like that of
red cherries or currants; however, grapes
grown in warmer climates present juicier
fruit, like that of plums, strawberries, raspberries, and blackberries as a direct result
of ripeness levels and sun exposure.
I’ve also written about terroir, or the microclimate of the region in which the grape
grows. The prevalent winds, irrigation, and
type of soil all influence the development
of the grape, its sugars and acids, and of
course, flavors.
So, let’s explore where the other aromas
and tastes originate. The array of flavors
you find in wine can be credited to three
primary areas: the grape itself, the climate
where the grape is grown, and the winemaking process.
The Grape
Did you know that there are about 5,000
different varieties of grapes, but only
about 100 are used in wine production?
Each grape comes with its own unique
compounds within the skin waiting for fermentation. Within grapes, there are three
November 2015 ❖ Julien’s Journal ❖ 45