How wine is made?

The production of wine

The long-term average annual production in the Czech Republic is in the region of 600,000 hectolitres of wine. Production and consumption of rosé wines is on the rise, moderately but steadily.

Raw material for the production of wine
The basic raw materials for the production of wine are the freshly picked wine grapes. Grapes are picked in the Moravian and Czech vineyard generally from the end of August (very early-ripening grape varieties) up until the end of November (late-ripening varieties). The exception to this is the harvesting of grapes in the winter months when there is frost for the production of ice wine. For simplicity’s sake the grape varieties for the production of wine can be divided into white (for the production of white wines) and black (for the production of red wines).

Destalking
After harvesting, the stems (stalks) are separated from the flesh (the berries) as fast as possible. Stalks are the waste matter and as a general rule they are used as fertiliser in the vineyards. Destalking must take place gently so as not to damage the pips inside the grapes, from which bitter elements could get into the wine. This separation of the berries (that is the juice including the crushed grapes) is referred to as the “must”.

Production of white wines
For white wines the must is pressed in briefly. The time between destalking and pressing may vary from “almost immediately” to several hours. In the majority of cases the must is left to macerate for 3 - 6 hours to obtain a better extraction of aromatic substances which are contained in the skins of the berries.

Most cultivated white grape varieties in the Czech Republic

Production of red wines
The production of red wines differs from that of white wines in that the must is pressed later, so it ferments together with the skins. It is precisely in the skins where the colouring matter is actually to be found, which during the course of fermentation is extracted and imparted to the must.

Most cultivated black grape varieties in the Czech Republic

Production of rosé wines
For rosé wines the must from black grapes is left to macerate for several hours so that the red colouring matter from the skins is partially released. Later it is pressed and processed in the same way as for white wine.

Pressing
Through pressing the must is separated from the skins – pomace. There are several different types of press – e.g. screw, hydraulic or pneumatic. The volume of pressed juice normally varies between 60% and 80%. After pressing the pure juice is then transferred into clarification tanks to settle (where solid particles are sedimented to the bottom) and is then racked off. At this stage chaptalisation (must enrichment) may occur whereby sugar is be added to simple quality wines in order to increase the level of potential alcohol (this is not allowed for wines with special attributes, such as kabinet, late harvest etc.). Should the sugar levels in red wines be required to be raised, this is done immediately after destalking so that the added sugar ferments along with the must.

Fermentation
During the production of white wines the must ferments (after pressing); for red wines the mass (the must together with the skins) is fermented first (the pressing begins after the fermentation is completed). Fermentation may begin spontaneously (thanks to the wild yeasts which are already present in the grapes in the vineyards). Nowadays, however, specially selected yeast cultures are being used more and more.
To put it simply, fermentation is the process of converting sugar into alcohol through the creation of carbon dioxide and heat. The current trend (especially in white wines) is to chill the fermenting must in such a way that the temperature does not exceed 18 – 20 °C. At this temperature many more natural aromatic substances are preserved in the wine than if the must were to ferment on its own accord at higher temperatures. The fermenting must is known in this country as “burčák” (known as Sturm or vin bourru in Austria and France respectively) and is a very much loved beverage hereabouts.
After the primary alcoholic fermentation red wines may usually undergo a secondary – malolactic fermentation, which converts the harsh malic acids into softer lactic acids.

Maturation, stabilisation, fining and filtration of wine
This is a process of manipulating the wine from the completion of the fermentation right up to its preparation for bottling (or to expedite in bulk for sale as wine on tap). It refers especially to the racking (separating wine from the deposited yeasts), the addition of sulphur dioxide to prevent oxidisation, the fining (removing the proteins and other unwanted substances) and possibly to further operations. A very important part of a wine’s stabilisation is filtration.
Maturation and stabilisation has a great influence on the character of a wine and requires a careful and expertly competent cellarmaster or oenologist. The fact whether or not a wine has been matured in stainless-steel vats or wooden barrels, in which case it undergoes a much stronger process of so-called micro-oxidation, also has an influence on the wine’s character. New wooden barrels also introduce further gustatory and aromatic material to the finished wine.