Wine Arcana

Concept

Pressing

Also known as Grape pressing

Pressing applies pressure to grapes or fermented grape solids to separate liquid from them. It is a decisive point in winemaking because the liquid collected early in the operation can differ from what is released later. A winemaker can keep those fractions apart and decide how much to combine.

Crushing opens berries; pressing extracts liquid from the resulting mass. Maceration describes the contact during which substances pass from solids into juice or wine. The three processes interact, but each answers a different question: how the berry opens, how liquid is recovered, and how much skin or seed contact it receives.

What goes into the press

Most white winemaking presses grapes before alcoholic fermentation, producing juice that ferments without the bulk of the skins. Conventional red winemaking presses fermenting or fermented material after a period of skin contact. The latter material has already undergone changes in temperature, alcohol concentration, and extraction.

Whole-bunch pressing puts intact bunches into the press. Stems can help form drainage routes through the load, although whole bunches occupy more space than crushed material. It is distinct from whole-cluster fermentation, in which bunches remain in the fermenter during fermentation.

For rosé, direct pressing describes prompt extraction from dark grapes with limited skin contact. It does not name a machine. Short maceration before pressing offers another route, while saignée draws liquid from a red-grape vat. A pneumatic press can therefore be used for a white wine, a direct-press rosé, or a red wine whose fermentation occurred before pressing.

Equipment and its operation

A traditional basket press compresses a load against a plate, allowing liquid to drain through openings around the basket. Modern hydraulic versions use a piston to drive that plate. The pressed solids form a cake; loading, emptying, and any breaking up of the cake are part of the working cycle.

A pneumatic membrane press inflates a flexible membrane to compress the fruit inside a vessel. Many programmes alternate compression with release and rotation, loosening the cake before pressure is applied again. Those movements help extraction, while also affecting how much solid material enters the liquid. A press described as “gentle” still needs a programme suited to the grapes and intended wine.

Equipment, load condition, and timing interact. In its account of making a Barossa Shiraz in 2015, the Australian Wine Research Institute described combining several fermentations into one suitable press load, adjusting cap management beforehand to accommodate their different times on skins. That is a documented logistical choice for that wine, rather than a universal maceration schedule.1. Peter Godden, “An exciting day – time for pressing!”, AWRI, 2015.

Free-run and press fractions

Free-run is liquid that drains without applied pressing pressure. After a red fermentation, draining it leaves a mass that still holds wine; pressing recovers more. Fresh crushed white grapes can likewise release juice before pressing begins. Intact bunches need their berries opened before much liquid can escape, so a whole-bunch pressing sequence does not begin under the same conditions as a tank of crushed fruit.

Later fractions can have more phenolic material, suspended solids, and a higher pH than earlier juice. These differences affect texture, clarification, and blending. Their magnitude depends on the grapes and extraction, so “press wine” is not a fixed sensory category. Keeping fractions separate allows the producer to assess what each contributes.2. Bruce Zoecklein, A Review of Méthode Champenoise Production, pressing discussion, especially pp. 17–19; fraction differences depend on the fruit and extraction conditions.

Champagne provides a clear example of fractionation: the first juice is designated cuvée and the subsequent fraction taille. The term cuvée has this specific pressing meaning alongside its broader use for a wine or blend. The region's pressing process keeps grape varieties and crus identifiable through reception and extraction.3. Comité Champagne, “Arrival at the pressing centre.”

Oxygen and the liquid leaving the press

Juice meets air in the press, collection tray, and transfer system. Protective handling limits oxidation, while some white-wine production intentionally oxidises juice before fermentation. Under that approach, oxidised phenolics can precipitate and be removed, reducing the resulting wine's later tendency to brown.

This is a treatment with conditions and trade-offs. It changes phenolic texture, and damaged or Botrytis-infected fruit introduces different enzyme activity. AWRI guidance specifically advises against hyperoxidation when Botrytis is present. Deliberately treating sound juice is consequently a different decision from allowing uncontrolled exposure throughout maturation.

Pressing leaves fine suspended material in the liquid. Settling and racking, or other clarification methods, determine how much of it continues into fermentation or ageing. The press ends bulk skin contact; it does not finish the wine.

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