Page 81 - Terčelj, Dušan. 2015. The Culture of Wine in Slovenia. Edited by Aleš Gačnik. University of Primorska Press, Koper.
P. 81
The Components of Wine
Gluconic acid
Can be the predominant acid in wines made from overripe grapes infected with Bo-
trytis cinerea – noble rot. It appears with the oxidation of glucose.
Succinic acid
Produced by yeast during fermentation up to the value of 1g per litre. Its salts are succinates.
Ascorbic acid or vitamin C.
Oxalic acid
Appears mainly in the form of oxalate salts.
D-Galacturonic acid
Is a component of pectin, which is the building material of the cells of grapes.
Phenolic compounds
Phenols are compounds consisting of a benzol ring, which can in nature only be found in
plants. They are divided into two large groups:
• phenolic acids with a single benzol ring or linked into two rings maximum;
• a ntocyanins and tannins, compounds in a molecule with three rings.
In grapes there are numerous phenolic acids, which give a bitter taste. They can bind
with organic acids into new compounds and with alcohols into aromatic substances. They
can be found mainly in grape skins and pips. The best known compound with one ring
is catechin, and with two rings resveratrol. The latter gives the skin rot resistance and is
beneficial to man as it prevents the blocking of veins, i.e. cardiovascular diseases. The
researcher Urška Vrhovšek from the Agricultural Institute of Slovenia has ascertained that
Modra Frankinja26 is particularly rich in resveratrol.
Antocyanins
give red wines their colour. Each variety of grapes contains different quantities of
individual antocyanins and thus a different shade of red. Their quantity depends on
the variety of grapes, as well as on their maturity and health condition and the extrac-
tion techniques used. Antocyanins are in nature bound to one molecule of glucose in
Vitis vinifera and with two molecules of glucose in the American grapevine and its
hybrids. Thus with respect to red wines we can chemically differentiate between the
noble European varieties and hybrids with American varieties, which are more resist-
ant to disease. Acids can bind to the glucose in antocyanins, creating new compounds
called acylated forms. Antocyanins, which give colour to red wine, can be coloured or
colourless. At lower acidity and a higher redox value, i.e. oxidation-reduction potential,
they have a stronger colour as their level in the coloured version is higher.
In the skin and later in the must antocyanins appear in free form. They quickly travel
from the skin to the must as they are both water and alcohol soluble, especially at higher
temperatures. In must they bind to oxygen and oxidise, but they also quickly bind to
26 V rhovšek, Urška: Bioaktivne polifenolne spojine grozdja in vina (Bioactive polyphenolic compounds in
grapes and wine). In: Vino-hrana, zdravje 2000. Strokovni posvet. Zbornik referatov. Poslovna skupnost za
vinogradništvo in vinarstvo Slovenije, Celje 2000, pp. 42-56.
77
Gluconic acid
Can be the predominant acid in wines made from overripe grapes infected with Bo-
trytis cinerea – noble rot. It appears with the oxidation of glucose.
Succinic acid
Produced by yeast during fermentation up to the value of 1g per litre. Its salts are succinates.
Ascorbic acid or vitamin C.
Oxalic acid
Appears mainly in the form of oxalate salts.
D-Galacturonic acid
Is a component of pectin, which is the building material of the cells of grapes.
Phenolic compounds
Phenols are compounds consisting of a benzol ring, which can in nature only be found in
plants. They are divided into two large groups:
• phenolic acids with a single benzol ring or linked into two rings maximum;
• a ntocyanins and tannins, compounds in a molecule with three rings.
In grapes there are numerous phenolic acids, which give a bitter taste. They can bind
with organic acids into new compounds and with alcohols into aromatic substances. They
can be found mainly in grape skins and pips. The best known compound with one ring
is catechin, and with two rings resveratrol. The latter gives the skin rot resistance and is
beneficial to man as it prevents the blocking of veins, i.e. cardiovascular diseases. The
researcher Urška Vrhovšek from the Agricultural Institute of Slovenia has ascertained that
Modra Frankinja26 is particularly rich in resveratrol.
Antocyanins
give red wines their colour. Each variety of grapes contains different quantities of
individual antocyanins and thus a different shade of red. Their quantity depends on
the variety of grapes, as well as on their maturity and health condition and the extrac-
tion techniques used. Antocyanins are in nature bound to one molecule of glucose in
Vitis vinifera and with two molecules of glucose in the American grapevine and its
hybrids. Thus with respect to red wines we can chemically differentiate between the
noble European varieties and hybrids with American varieties, which are more resist-
ant to disease. Acids can bind to the glucose in antocyanins, creating new compounds
called acylated forms. Antocyanins, which give colour to red wine, can be coloured or
colourless. At lower acidity and a higher redox value, i.e. oxidation-reduction potential,
they have a stronger colour as their level in the coloured version is higher.
In the skin and later in the must antocyanins appear in free form. They quickly travel
from the skin to the must as they are both water and alcohol soluble, especially at higher
temperatures. In must they bind to oxygen and oxidise, but they also quickly bind to
26 V rhovšek, Urška: Bioaktivne polifenolne spojine grozdja in vina (Bioactive polyphenolic compounds in
grapes and wine). In: Vino-hrana, zdravje 2000. Strokovni posvet. Zbornik referatov. Poslovna skupnost za
vinogradništvo in vinarstvo Slovenije, Celje 2000, pp. 42-56.
77
