🍷 Wine press

A wine press is a machine that separates juice from grapes by pressure. Grapes can be juiced directly in a press, but more commonly they are first crushed by rollers so that juice can be collected more quickly. Pressing is done in several cycles, interrupted by crumbling of the press cake to open new paths for the juice. It is a critical operation in wine production: the equipment influences quality, yield and throughput, and low levels of suspended solids in the juice mean fewer solids have to be removed before fermentation.

Vertical basket presses with a central iron spindle were introduced around the 1830s and by the late 19th century were the predominant style. A ratcheting press nut, developed by Mabille in 1869, let one or two people press large quantities of grapes by hand. In 1856 Joseph Vaslin patented a horizontal press, and in the 1920s his grandson patented a rotating cylindrical horizontal plate press. Pneumatic presses use an inflatable diaphragm instead of plates: the first horizontal bladder press was introduced by Willmes in 1951, and the pneumatic tank (membrane) press, introduced in 1974, is now the dominant type, with capacities of up to 75 cubic metres available.

Pressing grapes for white wine is more challenging than pressing red grapes that have already been broken down by fermentation. There are no definitive independent published studies showing which membrane press configuration is superior.