How is wine made?

Different types of wine are produced with different technologies. Apart from the grape varieties used, the most significant difference between making red, rosé and white wines is when the juice is separated from the solid parts.

Making white wine

In making white wine, after the berries are crushed the juice is pressed out of the solids straight away, which is why white wine can – rarely, but even so – be made from blue grape varieties. How is that possible? In white winemaking the juice never meets the skins that contain the colouring matter; the winemakers extract only the pale or straw-yellow grape juice mentioned earlier from the berries, and ferment only that into wine – that is, the skins that give colour are not present in the process.

The stages of making white wine:

Making red wine

Making red wines begins with crushing the berries of blue grapes; then the juice and the solids (skins, seeds) ferment together, for up to several weeks, and “warm” – that is, using the heat released during fermentation. Colour and aroma compounds slowly dissolve out of the dark grape skins, and then the red wine is pressed out of the solids.

The stages of making red wine:

Making rosé wine

With rosé wines too, colouring matter – and therefore the presence of the skins – is needed, though in a more restrained amount, so that a wine in various shades of pink can be born. In this case, after crushing – and before pressing – the berries ferment together with the skins only for a very short time, just a few hours, at most 1–2 days; then comes pressing, and only the rosé-coloured juice is fermented further. If the winemakers did not do this, and left the juice in contact with the skins for longer, they would end up with red wine.

Fermentation and maturing

An important question is how the wine obtained as described above – whether red, rosé or white – is to be fermented and later matured. The most common methods are steel tanks and oak barrels, but wines made in other alternative ways (for example in clay vessels, so-called amphorae) are also occasionally found.

Steel-tank fermentation (reductive method)

The point of steel-tank fermentation and maturing, also known as the reductive method, is that – unlike wines made with the oxidative method, that is, matured in barrels – the wines are made in a closed system, with air completely excluded, in cooled conditions, in steel tanks. While during the oxidative method contact with air can bring about the wine's secondary, mature aromas, in wines made with the reductive method only the primary flavours, scents and aromas that come from the grape can be sensed. These wines are fresh, richly fruity, lower in alcohol and lighter in colour.

The reductive method is often also called cold-controlled fermentation, because the temperature of the stainless-steel tanks is kept, right up to bottling, at the appropriate temperature – mostly very low – and precisely regulated. With the reductive method the grapes are typically ripe but not overripe, and need very fast processing, since right after harvest the micro-oxidation processes can begin in the berries by which the must can lose some of its fresh and lively flavour compounds.

Oak-barrel fermentation (oxidative method)

Oak-barrel fermentation and maturing differs significantly from the steel-tank version in that the wine – right up to bottling – is in constant contact with oxygen, because air enters through the pores of the barrel while water and alcohol evaporate outwards. At the same time the wine becomes more concentrated and fuller-bodied, and the soluble components and flavour compounds of the oak “melt” into the wine, giving the barrel-aged batches a richer aroma profile and complexity.