Page 124 - Terčelj, Dušan. 2015. The Culture of Wine in Slovenia. Edited by Aleš Gačnik. University of Primorska Press, Koper.
P. 124
he Culture of Wine in Slovenia
wine. Only when, in the last century BC, Caesar occupied Galicia did the Romans adopt
the Celtic method of barrel-making and started using barrels in winemaking.
Oak wood is most suitable for barrels. In winemaking, oak is still irreplaceable in the
production of high quality wines. When making a barrel, the wood is heated on the inside
in order to bend the staves. Chemical changes occur in the wood. In order to understand
the changes appearing in the chemical composition of wine stored in new oak barrels, we
must first acquaint ourselves with changes that occur in this heating of oak wood. Chemical
substances from the wood are transferred to wine, giving it a unique character.
The chemical composition of oak wood is: cellulose, hemicellulose and lignin. Oak sub-
stances transfer to wine, but which components transfer depends on the type of oak and
the drying and heating method. The best results are achieved at a high temperature, at
225 °C. The wood must be heated evenly along the entire surface. With heating sugars, a
constituent part of cellulose, produce furane aldehydes and pentoses in the wood, which
form hemicellulose, producing aldehyde furfural or the higher alcohol furfurol, which both
have the aroma of rye bread crust or caramel, while lignin when heated produces volatile
phenols, aldehydes and ketones, which affect the aromatic properties of wine. Volatile
phenols contain strong aromatic substances, such as guayacol, the aroma of smoke, and
eugenol, the aroma of cloves. In addition, heating produces the benzo-aldehydes vanillin
and syringaldehyde, as well as cinnamic acid aldehydes and phenol ketones. In the oxidation
of fatty acids resulting from heating other aromatic substances are produced. Oak tannins
exist as esters of gallic and cinnamic acid with glucose. These transfer into wine, take part
A combination of old and new vessels in the Ptuj wine cellar, 2006.
Photo: Aleš Gačnik.
in oxidation-reduction reactions and produce a bitter taste, but they greatly decompose
during heating. Octalactones, already present in the non-heated state, produce the flavour
of wood. These chemical changes in the wood, transferring to the wine and changing its
composition, show just what their influence is on wine’s quality and character.
120
wine. Only when, in the last century BC, Caesar occupied Galicia did the Romans adopt
the Celtic method of barrel-making and started using barrels in winemaking.
Oak wood is most suitable for barrels. In winemaking, oak is still irreplaceable in the
production of high quality wines. When making a barrel, the wood is heated on the inside
in order to bend the staves. Chemical changes occur in the wood. In order to understand
the changes appearing in the chemical composition of wine stored in new oak barrels, we
must first acquaint ourselves with changes that occur in this heating of oak wood. Chemical
substances from the wood are transferred to wine, giving it a unique character.
The chemical composition of oak wood is: cellulose, hemicellulose and lignin. Oak sub-
stances transfer to wine, but which components transfer depends on the type of oak and
the drying and heating method. The best results are achieved at a high temperature, at
225 °C. The wood must be heated evenly along the entire surface. With heating sugars, a
constituent part of cellulose, produce furane aldehydes and pentoses in the wood, which
form hemicellulose, producing aldehyde furfural or the higher alcohol furfurol, which both
have the aroma of rye bread crust or caramel, while lignin when heated produces volatile
phenols, aldehydes and ketones, which affect the aromatic properties of wine. Volatile
phenols contain strong aromatic substances, such as guayacol, the aroma of smoke, and
eugenol, the aroma of cloves. In addition, heating produces the benzo-aldehydes vanillin
and syringaldehyde, as well as cinnamic acid aldehydes and phenol ketones. In the oxidation
of fatty acids resulting from heating other aromatic substances are produced. Oak tannins
exist as esters of gallic and cinnamic acid with glucose. These transfer into wine, take part
A combination of old and new vessels in the Ptuj wine cellar, 2006.
Photo: Aleš Gačnik.
in oxidation-reduction reactions and produce a bitter taste, but they greatly decompose
during heating. Octalactones, already present in the non-heated state, produce the flavour
of wood. These chemical changes in the wood, transferring to the wine and changing its
composition, show just what their influence is on wine’s quality and character.
120
