Pressing (wine)

Lore & Background

The earliest wine press was likely the human foot or hand, crushing grapes into a bag or container for fermentation. The pressure from these manual means was limited, producing pale wines. The ancient Egyptians developed a sack press made of cloth squeezed with a giant tourniquet. The ancient Greeks and Romans built large wooden presses using beams, capstans, and windlasses, which evolved into the basket press used in the Middle Ages by nobility and the Catholic Church. Church records show feudal tenants paid a portion of their crop to use a landlord's press, as pressing could add 15–20% more volume than manual treading. Machine pressing became widespread in the 17th and 18th centuries as winemaking shifted toward heartier wines for aging and transport. In the 20th century, presses advanced from vertical basket presses to horizontal presses with pressure applied at one or both ends or via an airbag or bladder. These are categorized as batch presses, which must be emptied between loads, and continuous presses, where a belt or screw subjects grapes to increasing pressure. Modern presses can be enclosed to reduce oxygen exposure, and some can be flushed with nitrogen for an anaerobic environment; many are computerized to control pressure and cycles.

Reader's Guide

The timing of pressing and the methods used influence many winemaking decisions. In white wine making, pressing happens immediately after harvest and crushing, and the key decision is how much pressure to apply and how much pressed juice to use alongside free-run juice. Some grape varieties, such as Sémillon and Aurore, release juice easily with little pressure, while others like Catawba require more pressing. In red wine production, the decision of when to press is critical because it ends maceration and phenolic extraction. Winemakers may press when the wine reaches complete dryness, or earlier (e.g., at 3–8 brix) based on taste for balanced tannins. In cool years with under-ripe grapes, pressing early (e.g., at 15 brix) is sometimes done—a process Australians call short vatting—to avoid harsh green tannins. In warm years, extended maceration may delay pressing for up to a month after fermentation. Pressed juice often requires additional treatment, such as acid adjustments, extended settling, extra racking, and fining agents. Pectolytic enzymes may be used during maceration to break down cell walls and aid clarification. The amount of suspended solids from pressing affects filtering decisions, as high solids can clog filters.

Did You Know?

• Free-run juice accounts for approximately 60–70% of the available juice in the grape berry and does not require pressing.
• In Champagne and other sparkling wine regions, grapes are traditionally whole-cluster pressed with stems included to produce a lighter must low in phenolics.
• The ancient Egyptians developed a sack press made of cloth that was squeezed with a giant tourniquet.
• Some modern presses can be flushed with nitrogen to create a completely anaerobic environment for white wine making.