PRESSING
Pressing centres are very strictly regulated, in line with more than 20 approval criteria that were introduced in 1987. These cover pressing and racking capacity; daily press loads; type of press used; pressing and sulphuring; and hygiene standards.
On arrival at the pressing centre, each delivery of grapes is weighed and recorded. Every 4,000 kg ‘marc’ (traditional unit of measurement for a press-load of grapes) is numbered and recorded in the ‘carnet de pressoir’ (pressing logbook), noting details of grape variety, cru and destination (whether retained by the winegrower or sold to a Champagne House). The grapes are also tested for compliance with the minimum alcohol content by volume that is specified for the vintage in question.
The production of white wine from predominantly black-skinned grapes (two-thirds of the harvest) depends on five basic principles: pressing immediately after picking; whole cluster pressing; a gentle, gradual increase in pressure; low juice extraction; and fractionation (the clearer, purer juices that are drawn off at the beginning of pressing are separated from those produced at the end).
Juice extraction is strictly limited to 25.5 hectolitres per 4,000kg marc, separating the first pressing juice (the cuvée, representing 20.5hl) from the second (the taille, representing 5hl). Each has quite specific characteristics. The cuvée is the purest juice of the pulp – rich in sugar and acids (tartaric and malic). Cuvée musts produce wines with great finesse, subtle aromas, a refreshing palate and good aging potential. The taille is also rich in sugar, but acid content is lower while mineral content (especially potassium salts) is higher, along with colouring agents. Taille musts produce intensely aromatic wines – fruitier in youth than those made from the cuvée but less age-worthy.
Champagne presses range in capacity from 2,000 to 12,000 kilos of whole grapes. Manually operated, vertical basket presses were standard throughout the region until the late 1980s, and still account for some 28% of plant. The introduction of mechanical methods of ‘retrousse’ (the breaking-up of the press cake between cycles) then led to the increasing use of horizontal presses with a lateral membrane, angled pressing plates and a rotating press pan. Horizontal presses these days are computer-controlled, with a multi-function operating system.
If rosé Champagne is made via maceration, destemmed black-skinned grapes are left to macerate in a tank until the desired colour is achieved (24-72 hours).
Bin washing is compulsory after each separate press load. As part of their commitment to sustainable viticulture, the authorities in Champagne specify methods for the proper management of pressing waste products. Solid residues left over after pressing (the ‘aignes’) are sent for distillation, and winery wastewater (used for cleaning in the course of pressing) is recycled and treated so as to avoid any risk of environmental pollution.