Pressing (wine)

There are exceptions, such as the case of sparkling wine production in regions such as Champagne where grapes are traditionally whole-cluster pressed with stems included to produce a lighter must that is low in phenolics.

Some grape varieties, such as Sémillon and Aurore have very "liquidy" pulps that releases juice easily without needing much pressure that could risk tearing the skins.

Some winemakers use the decreasing sugar level (such as brix measurement) scale and press once the wine has reached complete dryness.

In warmer years, the tannins may be full ripe or "sweet" and the winemaker may decide to do a period of extended maceration and not press the grapes for as long as a month after fermentation has completed.

Grape pulp contains a lot of pectins that create colloid coagulation with these solids that will make the wine difficult to stabilize.

Some winemakers will use pectolytic enzymes during the maceration process to help break down the cell walls to allow the release of more juice freely.

[3] The earliest wine press was likely the human foot or hand, crushing and squeezing grapes into a bag or container where the contents would ferment.

Eventually humans discovered that more juice could be extracted and potentially a better wine could be produced if they developed ways of pressing.

It began with the ancient Egyptians who developed a "sack press" made of cloth that was squeezed with the aid of a giant tourniquet.

[9] There are many church records that showed feudal land tenants were willing to pay a portion of their crop to use a landlord's wine press if it was available.

[10] Machine pressing became even more widespread in the 17th and 18th century as the style of winemaking in France and other parts of Europe was shifting towards heartier wines that could age and survive long transport voyages overseas.

Additionally, many of today's modern presses are computerized, which allows the operator to control exactly how much pressure is being applied to the grape skins and for how many cycles.

The more the grape skins are torn or scoured, the more phenolic compounds and tannins that are extracted, which can increase the harshness of the wine.

This can be a significant advantage for a high volume winery compared to batch presses that often only process 1 to 5 tonnes an hour.

Often winemakers will keep free-run and pressed juice separated for most of the winemaking process including malolactic fermentation and barrel aging with the options to later blend between them to make the most complete, balanced wine, bottle separately under different labels and price tiers or to discard/sell off the pressed fractions to another producer.

[3] The extent of these differences will be magnified or minimized based on the initial condition of the fruit after harvest (with moldy, damaged, sun-burnt or botryized grapes producing stark differences between free-run and pressed juice), the type of press used, the amount of pressure involved and the overall amount of movement that the grapes are subject to that could impact how much the skins and seeds are scoured and torn.

Even some red wine producers (most notably Pinot noir) will use this type of pressing to avoid harsh tannins or "green-ness" that may come from under ripe grapes.

According to Pérignon (Godinot), the free run vin de goutte was considered too delicate and lacking on its own to make fine Champagne and it was sometimes discarded or used for other wines.