To safeguard the quality of the grapes, they have to be moved to the pressing center as soon after harvesting as possible. If the wait is too long, the grapes begin to undergo a self-processing process. This can lead to maceration and oxidation and can also lead to colouring of the pressed grape juice or must. Pressing the grapes straight after harvest is important because it helps bring out the natural expression of the grape. Grape pressing must take place a maximum of 6-8 hours after the grapes arrive from the vineyard. During the harvest presses are run 24 hours a day.
Location
All champagne growers who make and market their own champagne are classified by the Comité Champagne as Récoltant Manipulant (RM). All RM by definition must have their own grape press. The press is traditionally located as close as possible to the growers vineyards and usually on the growers premises.
The Press
All aspects of champagne grape pressing are strict controlled by guidelines published in 1987. Some producers have wooden presses and some have computer controlled high-tech presses. Either way, almost all producers locate their press on the ground floor so that after pressing gravity takes the must, down to storage vats located below ground below the grape press.
Grapes are pressed individually by type and vineyard and the musts from each press are carefully recorded and stored in separate tanks.
The pressure of the press is kept low (1kg/cm2) to prevent the must being coloured by the skin of the grapes. If red grapes are being pressed, to ensure the must remains white the juice has to be separated from the grape skin (exocarp), shortly after pressing. If rosé is being made the must can be left in contact with the red grape skin for some time, usually 24 – 72 hours. An alternatively method of making rosé is to add a little red wine to the finished champagne.
The Process
The “marc” is the standard unit of measure for press-load. Grape presses can press = 4000kg (4 tons) of grapes = 1 marc
The permitted press yield is: 102 litres of must from 160kg of grapes.
The aim of pressing is to press 2 qualities of must:
- Cuvée – or first 3 presses. Made of the purest juice of the pulp, rich in sugar and acid. It produces wine of great finesse, subtle aromas, with a refreshing palate and good aging potential.
- Taille – is produced after the cuvée has been produced using up to 3 presses. It is produced at a slightly higher pressure than the cuvée. The sugar and acidity are comparatively lower than the cuvée. The must exhibits more structure, is a richer colour and has more astringency. Up to 500 litres of taille can be produced.
The cuvée is extracted by 3 successive pressings. Between each press the crushed grapes directly under the press plates, called the ‘press cake‘, are raked away and replaced with less crushed grapes from the edges of the basket. The 3 press cuvée cycle produces:
- 1025 litres from the 1st press
- 615 litres from the 2nd press
- 410 litres from the 3rd press
The total press yield for the cuvée from each press is a maximum of 2050 litres. Once the cuvée has been extracted, the grapes may be pressed again up to 3 times to produce a maximum of 500 litres of taille. The whole pressing cycle lasts approximately 3 hours.
Not all RM growers use all of the fractions from the cuvée, some like Ployez-Jacquemart only use the first press from the cuvée to make their champagne and they sell the second and third presses to one of the Négociant Manipulant (NM) Grand Marques like G.H. Mumm.
Other Products
After the cuvée and taille have been produced the grapes can be pressed again but the produced must has to be sent for distillation into alcohol e.g. Ratafia which is about 18% alcohol. After each pressing cycle, the left-over skins, stalks and seeds in the bottom of the basket may be collected and fermented then distilled to produce a grappa-like spirit called Marc de Champagne which is around 40% alcohol.
The freshly pressed cuvée and taille musts also contain some skin, stalks and seeds. The fresh musts descend by gravity down into separate open tanks below the press called belons. At this stage, a small quantity of sulphates may be added to the musts which helps maintain must integrity. The addition of sulphates also has the added bonus of aiding the precipitation of solids out of the musts.
Clarification
From the belons the must is transferred into clean (often steel) tanks for clarification or débourbage. The must is left to settle under gravity for between 12 to 24 hours. During this time the solid cellulosic material flocculates to form clumps and sink and, solids also sediment and sink to the bottom by gravity. A muddy layer forms on the bottom of the tank. Upon completion of the clarification process, the must is transferred into another tank for the next stage in the process, primary fermentation.