Page 79 - Terčelj, Dušan. 2015. The Culture of Wine in Slovenia. Edited by Aleš Gačnik. University of Primorska Press, Koper.
P. 79
The Components of Wine
Water
Grapevines draw water from the soil and with it minerals and nitrogen, as well as the
substances polluting the soil. Water affects the composition of wine and with nuclear
magnetic resonance it is possible to ascertain where a particular wine originates from, i.e.
its provenance.
Sugar
Grape juice contains two main sugars in the form of hexoses, i.e. sugars with six carbon
atoms in a molecule: glucose or grape sugar and fructose or fruit sugar. These two sugars
can ferment into ethanol and carbonic acid. As by their nature they are aldehydes, they can
oxidise and bind with sulphur dioxide (the sulphurisation of must or wine). In addition to
these two sugars, there are also small quantities of pentoses with five carbon atoms in a
molecule, which cannot be fermented by yeast.
On the basis of the quantity of residual sugar they contain, wines are divided into:
• dry wines, which have up to 4g of residual sugar per litre
(the sugar can almost not be tasted);
• s emi-dry wines, which have 4-12g of sugar per litre
(the wine is not yet sweet, but the sugar does give it fullness)
• s emi-sweet wines, which have 12-45g of residual sugar per litre
(the wine tastes slightly sweet)
• sweet wines, which have over 45g of residual sugar
(these wines have a sweet flavour).
Polysaccharides
In the noble varieties of the European grapevine, saccharose appears in very low quanti-
ties (up to 0.5g per litre), while in American varieties and their hybrids with European
varieties, this quantity is higher. Saccharose as a disaccharide consists of D-glucose and
D-fructose.
Glucose molecules can combine into larger molecules of new compounds when still in the
grapes, imparting fullness. Glucose compounds give starch and cellulose.
Acids
Acids affect the taste of wine: various acids give wine different acidity. In grape juice there
are organic acids, releasing hydrogen ions (H+). These give wine its acidity, measured with
a pH value, which is usually between 3 and 3.5. The acidity of a must or wine must be in
harmony with other substances, mainly sugars and tannins. Acidity influences numerous
bio-chemical processes. The stability of other substances, such as proteins, also depends
on the pH value. These are the most important organic acids in grape juice:
75
Water
Grapevines draw water from the soil and with it minerals and nitrogen, as well as the
substances polluting the soil. Water affects the composition of wine and with nuclear
magnetic resonance it is possible to ascertain where a particular wine originates from, i.e.
its provenance.
Sugar
Grape juice contains two main sugars in the form of hexoses, i.e. sugars with six carbon
atoms in a molecule: glucose or grape sugar and fructose or fruit sugar. These two sugars
can ferment into ethanol and carbonic acid. As by their nature they are aldehydes, they can
oxidise and bind with sulphur dioxide (the sulphurisation of must or wine). In addition to
these two sugars, there are also small quantities of pentoses with five carbon atoms in a
molecule, which cannot be fermented by yeast.
On the basis of the quantity of residual sugar they contain, wines are divided into:
• dry wines, which have up to 4g of residual sugar per litre
(the sugar can almost not be tasted);
• s emi-dry wines, which have 4-12g of sugar per litre
(the wine is not yet sweet, but the sugar does give it fullness)
• s emi-sweet wines, which have 12-45g of residual sugar per litre
(the wine tastes slightly sweet)
• sweet wines, which have over 45g of residual sugar
(these wines have a sweet flavour).
Polysaccharides
In the noble varieties of the European grapevine, saccharose appears in very low quanti-
ties (up to 0.5g per litre), while in American varieties and their hybrids with European
varieties, this quantity is higher. Saccharose as a disaccharide consists of D-glucose and
D-fructose.
Glucose molecules can combine into larger molecules of new compounds when still in the
grapes, imparting fullness. Glucose compounds give starch and cellulose.
Acids
Acids affect the taste of wine: various acids give wine different acidity. In grape juice there
are organic acids, releasing hydrogen ions (H+). These give wine its acidity, measured with
a pH value, which is usually between 3 and 3.5. The acidity of a must or wine must be in
harmony with other substances, mainly sugars and tannins. Acidity influences numerous
bio-chemical processes. The stability of other substances, such as proteins, also depends
on the pH value. These are the most important organic acids in grape juice:
75
