Agriculture Reference
In-Depth Information
14
The Science of Wine
At its core, the theory of making wine (also beer and bread) is
nothing more than the conversion of sugar into ethyl alcohol
and carbon dioxide by the enzymes in yeast:
glucose → ethyl alcohol + carbon dioxide + energy
C6H12O6 → 2(CH3CH2OH) + 2(CO2) + Energy
Using the foregoing formula based upon the molecular
weights
45
of the compounds, 180 grams of glucose will be
converted into 92 grams of ethyl alcohol and 88 grams of
carbon dioxide. This means that the yield of alcohol, by
weight, in a perfect fermentation is 92/180 or 51%, and that
nearly half of the weight of the sugar is lost in the form of
carbon dioxide gas.
The density of glucose is 1.54 g/cm3, so the volume occupied
by 180 grams of glucose is 180/1.54 or 116.88 cm3. The
density of ethyl alcohol is .789 g/cm3, and the volume
occupied by 92 grams of ethyl alcohol is 92/.789 or 116.6
cm3.
In other words, even though nearly half of the mass of sugar
is lost in the form of carbon dioxide gas, the volume of the
solution stays so nearly the same as to be indiscernible
without resorting to very precise measurements.
Furthermore, the percentage of alcohol in beverages is not
measured by mass, but rather by volume. This means that the
