Definition: Pressing (in Champagne)

Article taken from the recommended website for learning about Champagne - UMC - Grandes Marques et Maisons de Champagne

As soon as they are picked, the bunches of grapes are taken to the "vendangeoir" where the presses are located. The grapes are pressed there, vintage by vintage, grape variety by grape variety, and never wait more than six to eight hours, day or night. It is at this point that most of the harvest is taken over by the Champagne Houses. The buyer (or their representative on site) checks, in accordance with established practice, that the grapes are "healthy, fair and marketable". The actual price paid for the grapes is the result of a freely negotiated agreement between each Champagne House and its grape suppliers. However, winegrowers and Maisons jointly observe the price level resulting from the balance between supply and demand in each cru. This indicative reference is set for several years and takes into account various factors resulting from an economic observatory. Pressing costs, brokerage commissions and ancillary premiums are also indicated.

The price, negotiated by mutual agreement, varies according to the quality of the grapes. It is therefore directly linked to the exposure and terroir. The "cru scale" gives the percentage ranking of the 321 communes producing grapes in the defined area of the "Champagne" appellation. Champagne grapes are "the most expensive in the world" because each plot is cultivated like a small garden with a minimum of 8,000 vines per hectare. The equivalent of all the fruit from a single vine is needed to produce one bottle of this sparkling wine. As producers and winegrowers are always seeking the best quality, the pressing technique is governed by strict regulations that are frequently updated. The bunches of grapes must be placed in the press in a completely intact state, which currently rules out any mechanisation of the harvest. The yield is limited to 102 litres of must per 160 kg of pressed grapes. The separation of the juices at the outlet of the press must allow 20.50 hl of "cuvée" and 5 hl of "taille" to be extracted. Pressing facilities must comply with precise specifications in order to obtain approval. These rules are designed to ensure maximum respect for the grapes, so that the colour contained in the skin of black grapes (Pinot Noir and Pinot Meunier) does not colour the must. Similarly, these requirements help to preserve the analytical and organoleptic characteristics that are crucial in the process of making sparkling white wine during juice extraction. The presses used must also meet strict standards: loading must be easy, quick and with a low drop height for the grapes. The pressing surface must be large. Juice extraction must be carried out at 90 degrees to the pressure axis, so as to promote self-filtration of the must, and at low pressures (less than 1 kg/cm²) to avoid any colouring of the juice. The establishment of specifications applied by manufacturers to control consoles. The pressing centre is a key location for obtaining the "Champagne" appellation. It must comply with very specific specifications defined by Champagne professionals and the Institut National des Appellations d'Origine (INAO). The premises, the press, the settling tanks and everything else that makes up this place must obtain the approval defined by the Champagne Interprofessional Organisation within the framework of a Quality Charter, which was adopted in 1987.

The use of specific presses also involves strict standards. The equipment used for pressing is extremely diverse and has continued to evolve over time. As a result, the quality of Champagne wine is constantly improving. Here again, this technique requires strict expertise: only whole bunches are loaded and pressed; the juice is extracted gradually with a slow increase in pressure; each bunch is handled delicately without bruising it; the juice is properly self-filtered through the pomace cake; and oxidation of the must is avoided. These technical requirements are combined with human imperatives: seeking optimal continuity in the sequence of operations, in particular by reducing downtime, in order to avoid any storage of the harvested grapes. It is also a question of reducing the arduous nature of the operations through greater automation. Five types of presses are used in Champagne, each operating in a different way:

1) The traditional vertical press with a fixed vat (the lower part of the press, in which the must that flows out during pressing is collected). These presses still account for almost half of the total number of presses and press a third of the grapes in Champagne. The main manufacturers are Coquard, Darc, Dol-lat and Marmonier. A vertical push plate crushes the grapes placed in a round or square cage. The maie is fixed and the juice flows out from the sides and base through the "marc cake". The "retrousses" or operation of bringing the edges of the cake (or mass of less crushed grapes) back to the central part of the press is done manually with a fork. These presses have a load capacity of 2,000 or 4,000 kg of grapes in whole bunches.

2) The horizontal mechanical plate press. The juice is extracted by squeezing the grapes between two vertical plates mounted on a central screw. The rotation of this screw in the opposite direction to that of the cage saves time and limits manual intervention. The horizontal cage is perforated to allow the juice to flow out. Recent models called "Champagne" regulate the increase in pressure in stages, depending on the flow of juice. Introduced in Champagne in the mid-1950s, the "Vaslin" press was the first automatic press. It has a loading capacity of 2,000, 4,000, 8,000 or 12,000 kg of whole bunches. They account for a third of Champagne's presses and press a quarter of the grapes.

3) The horizontal pneumatic press with a central bladder. Manufactured by Mabille, it can hold a load of 6,000 kg of whole grapes. It was the first press to use a compressed air source: an inflatable air chamber, located along the central axis of the device, exerts direct pressure on the marc. Despite its undeniable pioneering genius, it remains little used due to the risk of bladder puncture and poor self-filtration of the must.

4) The horizontal pneumatic press with a side membrane. This type of press comes in four versions that can handle loads of 2,000, 4,000, 8,000 or 12,000 kg of whole grapes. There are many manufacturers: Bücher, Diemme, Jouglet, Mazancourt, Péra, Siprem and Willmes. Pressure is no longer applied by means of an axial bladder, but by a synthetic membrane fixed diametrically to the cage. The vat is closed but equipped with drains to allow the juice to flow into a collector. Pressure can be applied using compressed air or water. The pressing programme is relatively automated.

5) The horizontal hydraulic press with lateral thrust and rotating vat. This represents the most recent technical innovation in the field. It was introduced in 1985 and is manufactured by Coquard. It is available in three versions with a capacity of 2,000, 4,000 or 8,000 kg of whole bunches. It operates on the principle of lateral pressure, using two plates equipped with hydraulic jacks. The grapes are turned over by simply moving the plates backwards, followed by a 90° rotation of the vat. The juice flows out from the bottom, through the perforated vat and from the sides of the openwork cage. Unloading is automatic and the pressure levels are adjusted at the start of the programme. These last two types of horizontal presses account for a quarter of the Champagne region's stock and press a third of the harvest. Their use is growing.

The press must be operated with regular, gradual and slow increases in pressure. It is necessary to limit the number of times the grapes are turned (during pressing, the grapes are brought back to the centre of the press). Manual operation is best suited to this delicate task, but it requires constant vigilance, which is difficult to maintain given the fast pace of the harvest. To resolve this difficulty, while continuing to meet the slow and gradual extraction standards imposed in Champagne, the technical services of the A.V.C., in agreement with Champagne professionals and press manufacturers, have established specifications defining the limits of duration and pressure to be exerted on the grapes. This led to the creation of automatic consoles, which have the advantage of storing several programmes that the press operator can apply depending on the grape variety and ripeness. There are now three types of consoles that meet these specifications: first-generation consoles with pre-set programmes (manufacturers: Bücher, Coquard, Diemme, Jouglet, Magnum, Mazancourt, Péra, Siprem, Willmes). Everything is pre-set: choice of pressure levels, choice of optional levels, duration of maintenance and intensity of retraction. A programme is selected at the start, which can be modified manually at any time during pressing, depending on the characteristics of the grapes. Second-generation consoles, with programmes for juice flow and timing (manufacturers: Diemme, Jouglet, Péra, Siprem, Willmes). The duration of each press is automatically linked to the frequency of pressure recovery at a given set point, without manual intervention. Two times are predefined by the programme: the recovery time and the maximum duration of maintenance at a given set point. The intensity of the presses is predetermined. Finally, there are third-generation consoles with a programme for measuring the actual juice flow rate (manufacturers: Bücher and Péra). Tested during the 1994 harvest by the A.V.C., a console of this type (and thanks to a flow meter installed downstream of the press) makes it possible to measure the actual juice flow rate and deduce the volume drained. Software automatically determines the holding times at each pressure level, the optional passage through stages at the end of pressing and the intensity of the retractions. This console ensures a high level of safety.

Juice fractionation: the aim of pressing is to extract the juice from the grapes. The bunches are very fragile and must be handled with great care. The basic principle is simple: start by placing a "marc" of grapes, or approximately 4,000 kg of whole bunches, in the vat (or loading area of the press). Then, the trays, secured by metal struts or brackets, are subjected to gradual, intermittent pressure, which causes them to descend onto the bunches. The juice then flows between the press's racks. The very first juice (or "self-pressing") results from the natural pressing of the grapes against each other during loading. It can represent 100 to 150 litres. It is often discarded when it contains impurities or juice that has oxidised during handling since the grapes were picked. The first juice (or "cuvée") is obtained by three successive and discontinuous pressings (or "serrages" or "serres"). The first pressing generally yields around 10.25 hl in the "belon" (a reception tank made of cement, enamelled steel or stainless steel). To obtain the authorised 20.50 hl, the "retrousse" is carried out, an operation which consists of breaking the edges of the "cake" (or mass of less crushed grapes) located on the periphery and which have therefore been subjected to lower pressure. Two new presses (or "retrousses") are used to obtain the additional quantity of juice (6.15 hl and 4.10 hl) that makes up the cuvée. After these three presses, a third retrousse is carried out and a third juice (or "taille") of 5 hl is extracted. This cycle may include 2 or 3 presses depending on the grapes. The quality of a wine results from its sugar, tartaric and malic acid content, as well as its potassium content. These elements are found in the pulp, whose sensitivity to bursting is divided into three zones: the intermediate zone (1), rich in sugar and acid; the central zone (2), rich in tannin and malic acid; and the peripheral zone (3), rich in potassium. The purpose of fractional pressing is to extract the compounds present in the pulp. Zone 1 bursts first, giving the cuvée a different chemical composition from the taille. It is richer in sugar and acid, more balanced and has a more developed bouquet. A cuvée must be free from tannins and oxidation. If the taille is fruitier, less acidic and slightly tanned, it is because the must has absorbed minerals and colouring agents, colloids and albuminoid substances. The cuvée and taille are therefore vinified separately. This focus on quality over quantity is evident at every stage of the Champagne sparkling wine production process, from vine cultivation to cuvée production. Once the cuvée and taille have been pressed, the remaining juice is known as "rebêches" and is sent directly to the distillery to provide the alcohol that wine producers are required to supply by law. Finally, the residue from the pressing, the skins, stalks and seeds, known as "aignes", are distilled after fermentation to obtain Champagne marc.

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