Page 85 - Terčelj, Dušan. 2015. The Culture of Wine in Slovenia. Edited by Aleš Gačnik. University of Primorska Press, Koper.
P. 85
The Components of Wine
During the fermentation of red wines, phenolic substances are leached, i.e. colour and
tannins, which gives them their particular characteristics. Phenolic substances are not
stable, they keep combining. The colour and bitterness of red wine therefore keep changing.
While maturing, the colour takes on brownish hues and tannins turn into more pleasant,
less tart flavours.
The aromatic substances in grapes are numerous, but only a few are perceivable by our
senses. Most of them – there are a few hundred in total – appear in such small quantities
that we can only identify them using gas chromatography, although together they still
affect the perception of the aromatic substances and give the aroma of wine its tone.
The primary aromas are the aromas of the grape variety. They appear in the skin and are
different in composition in each variety. They consist of various terpenes. Researchers have
already determined over seventy of these. Approximately 10 percent are in free form, giving
grapes their aroma, while the remaining 90 percent are bound to sugars and do not give an
aroma, as they do not vaporise at normal temperature, but are potential carriers of aroma if
we release them with enzymes. In addition to terpenes, grapes contain small quantities of
other aromatic substances. Some varieties have a stable aroma, such as Chardonnay, which
is, depending on its provenance, always recognisable. Other varieties are more sensitive
and give aromas of different intensity, depending on the conditions, such as Sauvignon or
Rhine Riesling. There are also varieties with exceptionally unstable aromas, such as Zelen.
Its aroma and the right conditions for the grapes to become aromatic have not yet been
determined. The essential properties of primary aromas are gentleness and the smell of
flowers and fruit. Aromas can be intensified by the maceration of crushed grapes for a few
hours even in white grapes varieties. The bound terpenes release glucose with the aid of
the enzyme ß-glucosidase. The enzyme is also synthesised by some strains of yeast. Some
S. cerevisiae strains of yeast contain enzymes that release bound terpenes into free ones,
which intensifies the aroma of a particular variety. There is also “aromatic yeast”, which
creates its own aroma that is not the aroma by which the grape variety is identified. On
the basis of terpene alcohols, which are specific to each variety, we can ascertain (with gas
chromatography) the variety of wine. In Slovenia, Mojmir Wondra has studied the aromatic
substances in Chardonnay wine and the influence of yeast on their composition during
fermentation. Primary aromas appear in grape skin and develop the highest concentration
just before the grapes reach full maturity. Let me list a few characteristic ones:
• coumarin – the aroma of grass (Sauvignon);
• terpinol – the aroma of elder flower;
• geraniol, linalool, citronellol – Muscat varieties;
• ionone – the aroma of violets (Traminec);
• the ester of octanoic acid – the aroma of blackberries (Modri Pinot (Pinot Noir),
Modra Frankinja);
• hotrienol – the aroma of peaches (Rhine Riesling);
• terpendiol – the aroma of roses (Traminec, Pinot Blanc);
• d iphenyl ketone – the aroma of raspberries (Refošk, Žametna Črnina, Teran).
81
During the fermentation of red wines, phenolic substances are leached, i.e. colour and
tannins, which gives them their particular characteristics. Phenolic substances are not
stable, they keep combining. The colour and bitterness of red wine therefore keep changing.
While maturing, the colour takes on brownish hues and tannins turn into more pleasant,
less tart flavours.
The aromatic substances in grapes are numerous, but only a few are perceivable by our
senses. Most of them – there are a few hundred in total – appear in such small quantities
that we can only identify them using gas chromatography, although together they still
affect the perception of the aromatic substances and give the aroma of wine its tone.
The primary aromas are the aromas of the grape variety. They appear in the skin and are
different in composition in each variety. They consist of various terpenes. Researchers have
already determined over seventy of these. Approximately 10 percent are in free form, giving
grapes their aroma, while the remaining 90 percent are bound to sugars and do not give an
aroma, as they do not vaporise at normal temperature, but are potential carriers of aroma if
we release them with enzymes. In addition to terpenes, grapes contain small quantities of
other aromatic substances. Some varieties have a stable aroma, such as Chardonnay, which
is, depending on its provenance, always recognisable. Other varieties are more sensitive
and give aromas of different intensity, depending on the conditions, such as Sauvignon or
Rhine Riesling. There are also varieties with exceptionally unstable aromas, such as Zelen.
Its aroma and the right conditions for the grapes to become aromatic have not yet been
determined. The essential properties of primary aromas are gentleness and the smell of
flowers and fruit. Aromas can be intensified by the maceration of crushed grapes for a few
hours even in white grapes varieties. The bound terpenes release glucose with the aid of
the enzyme ß-glucosidase. The enzyme is also synthesised by some strains of yeast. Some
S. cerevisiae strains of yeast contain enzymes that release bound terpenes into free ones,
which intensifies the aroma of a particular variety. There is also “aromatic yeast”, which
creates its own aroma that is not the aroma by which the grape variety is identified. On
the basis of terpene alcohols, which are specific to each variety, we can ascertain (with gas
chromatography) the variety of wine. In Slovenia, Mojmir Wondra has studied the aromatic
substances in Chardonnay wine and the influence of yeast on their composition during
fermentation. Primary aromas appear in grape skin and develop the highest concentration
just before the grapes reach full maturity. Let me list a few characteristic ones:
• coumarin – the aroma of grass (Sauvignon);
• terpinol – the aroma of elder flower;
• geraniol, linalool, citronellol – Muscat varieties;
• ionone – the aroma of violets (Traminec);
• the ester of octanoic acid – the aroma of blackberries (Modri Pinot (Pinot Noir),
Modra Frankinja);
• hotrienol – the aroma of peaches (Rhine Riesling);
• terpendiol – the aroma of roses (Traminec, Pinot Blanc);
• d iphenyl ketone – the aroma of raspberries (Refošk, Žametna Črnina, Teran).
81
