Press

How a press works

There are two main types of wine press in modern use. The basket press, an old-fashioned design with a wooden or metal cage and a screw-driven plate, is still used by some artisan producers for its gentle action and traditional feel. The pneumatic press, the workhorse of the modern wine industry, uses an inflated rubber bladder to push the grapes against the outer cage, gently squeezing out the juice.

A pneumatic press can be programmed to run a low-pressure cycle for the first half of the pressing, capturing the highest quality free-run juice, and a higher-pressure cycle for the second half, capturing the more phenolic pressed juice. The two fractions are often kept separate, with the first fraction going into the premium cuvée and the second going into a lower tier or being blended back at low proportion.

Pressing whole bunches

For sparkling wine, the grapes are usually pressed as whole bunches, without destemming, because the stems create channels for the juice to flow and reduce the extraction of harsh phenolics. This is called whole-bunch pressing, and it is the standard technique in Champagne and the UK.

For red wine, the press is used after fermentation, to separate the wine from the skins. The timing and pressure affect the tannin and colour of the final wine. A gentle press of a red ferment gives a softer, more elegant wine, while a hard press of a tough, tannic lot gives a more structured, more extracted wine.

Press fractions in the UK

UK producers are increasingly obsessed with the quality of their press fractions. The first 400 to 500 litres of juice from a tonne of grapes, known as the cuvée, is the most prized. The next 100 to 200 litres, the taille, is often blended back in or used for a different cuvée. The last 50 to 100 litres, the press wine, can be high in phenolics and is usually reserved for a still wine or distilled.

The same logic applies to red winemaking. The free-run wine, which flows out of the fermenter before any pressing, is the most elegant. The pressed wine, which requires force to extract, is more structured and tannic. Most UK producers blend the two in proportions that suit the style of the wine.

Cleaning and hygiene

Presses are notoriously hard to clean, because the press cage has hundreds of small channels and the bladder has many folds. A poorly cleaned press is a major source of microbial contamination, which can cause off-aromas, premature oxidation or stuck fermentations. UK producers devote significant time to cleaning, often with hot water, citric acid and dedicated cleaning chemicals, followed by a sanitising rinse.

A well-maintained press will give 20 to 30 years of service. A poorly maintained one will give years of headaches. Most UK wineries have a dedicated press operator and a strict daily cleaning routine.