FROM VINES TO PLEASURE

Grape production:
From planting vinestocks to collecting the grape juice

3. The pressing

      As soon as the bunches of grapes are picked, they are taken to the press-house ('vendangeoir'). They are then pressed growth-by-growth and grape-variety by grape-variety. They are never kept waiting for more than six to eight hours, day or night.
      It is at this moment that the Champagne Houses take over responsibility for most of the harvest. The buyer or his representative on site checks that, as per the established customary terms, the grapes are "healthy, loyal and tradable".
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Appendix: determining the selling price of the grapes

      The selling price of the grapes is a result of freely negotiated agreements between each Champagne House and its grape suppliers.

      The vine-growers and the Houses nonetheless do actively monitor the price level, which results from the balance of supply and demand in each growth. This indicative reference price is fixed for several years and takes into account numerous factors. It initially results from a detailed analysis of the economic situation. The cost of pressing, the wine broker's commission and the additional bonuses are also important elements.
 
      The price varies according to the quality of the grapes. It is consequently linked directly to both the exposure and the 'terroir'. The scale of growths ('l'échelle des crus') gives the classification as a percentage of the 321 communes that produce grapes in the area defined by the Champagne appellation.

      Champagne grapes are ‘the most expensive in the world’ because each parcel is cultivated like a little garden with at least 8,000 vines per hectare! It takes the entire fruit from one vine to produce a single bottle of Champagne.

      Houses and vine-growers are always striving for the best possible quality. The pressing techniques are governed by strict regulations that are frequently updated.

The grapes must be placed into the press intact.       The yield is limited to 102 litres of must per 160kg of pressed grapes.       Separating the juice as it leaves the press yields 20.5hl of 'cuvée' (the first pressing) and 5hl of 'taille' (the second pressing).

      . The press equipment must conform to a specific reference guide in order to obtain approval.

      These rules are established in order to protect the grape as much as possible. It is vital that the colour contained in the black grape skin (Pinot Noir and Meunier) does not tint the must. Similarly, when the juice is extracted, these rules preserve the analytical and organoleptical characteristics necessary for the production of a sparkling white wine.

      In addition, the presses used must conform to strict standards -

• The loading must be quick and easy with a short falling height for the grapes.

• The press surface area must be wide.

• A press must extract the juice with an axis set at 90 degrees to encourage the auto-filtration of the must and at low pressure (less than 1kg/cm2) to avoid discolouration.

• The manufacturers must establish a reference book for the operation panel.

• The pressing centre is the determinant place for obtaining the "Champagne" appellation. It must comply with a very specific reference guide defined by the professionals of Champagne and the INAO. The premises, the press and the vats used for settling the juice, as well as everything else in the centre, must obtain the consent of the Champagne Inter-profession as part of the quality charter adopted in 1987.

   C) Specific presses

      There is a great variety of equipment used for pressing and there continues to be ongoing development in this area to improve the quality of the wine used for Champagne. Once again this technique complies with a strict 'know-how':

• Only load and press whole bunches.

• Ensure progressive juice extraction with a steady increase in pressure.

• Handle each bunch delicately – to avoid bruising.

• Ensure a high level of juice auto-filtration through the press-cake.
  
  
• Avoid must oxidation.

      These technical requirements are combined with economic concerns in order to ensure the optimal flow in operations by reducing 'dead time' and to limit the tedious manual labour through the utilisation of advanced automation.

       Five different types of presses are used in Champagne:

1) Traditional vertical press with fixed press-pan
 
      These presses still account for almost half of the total and press a third of all Champagne grapes. The principal manufacturers are Coquard, Darc, Dollat and Marmonier.

A press-pan with a vertical chaser crushes the grapes, which are placed in either a round or square cage. The pan is fixed and the juice runs down the sides and through the base across the press-cake (the mass of less crushed grapes). The 'retrousses', an operation to return the edges of the press-cake towards the central part of the press, are done manually with a fork. These presses have a load capacity of 2,000-4,000kg of grapes in whole bunches

Pressing

Vidéo 1'40 min

2) Mechanical horizontal press with tray

      The juice is extracted by squeezing the grapes between two vertical trays assembled on a central screw. This screw rotates in the opposite direction to the cage. This saves time and limits the manual intervention. The horizontal cage has slots allowing the juice to run out. Recent models known as 'Champagne' gradually regulate the increase in pressure depending on the flow of juice.

      This was introduced into the Champagne region in the mid-1950s. With this machine, Vaslin constructed the first automatic press. It has a load capacity of 2,000; 4,000; 8,000 or 12,000kg of whole grapes. These presses account for one third of the Champagne presses in operation and press a quarter of the grapes.  

3) Pneumatic horizontal press with central bladder

      This type of press is built by Mabille and can contain a load of 6,000kg of whole grapes. It was the first press to utilise compressed air. An inflatable air chamber located along the central axis of the apparatus exerts direct pressure on the press-cake. Despite being an ingenious and undeniable forerunner to later developments, it is now seldom used due to the risk of puncturing the bladder and the mediocre auto-filtration of the mus

4) Pneumatic horizontal press with lateral membrane

      This type of press exists in four different versions, accepting loads of 2,000; 4,000; 8,000 or 12,000kg of whole grapes. There are numerous manufacturers - Bücher, Diemme, Jouglet, Mazancourt, Péra, Siprem and Willmes. The pressure is no longer exerted by the intermediary of an axial bladder, but by a synthetic membrane fixed diametrically across the cage. The vat is closed but is equipped with drains that ensure a flow of juice to the collecting tray. The pressure can be exerted either by compressing air or water. The pressing programme for this machine is relatively automated.

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5) Hydraulic horizontal press with lateral pressure and rotating press-pan

      This is the most recent technological innovation in this area. It was introduced in 1985 and is manufactured by Coquard. There are three different versions allowing loads of 2,000; 4,000 or 8,000kg of whole grapes. It functions on the principle of lateral pressure and has two trays with hydraulic jacks. The harvest is sifted by a simple backward movement of the trays followed by a rotation of 90° of the press-pan. The juice flows towards the bottom through the perforated press-pan and subsequently the slots in the sides of the cage. The unloading takes place automatically and the adjustment of pressure levels is central to the programme.

      The latter two types of horizontal presses represent a quarter of the Champagne fleet and press one third of the harvest. They are becoming increasingly popular.

D) The operation of the press

      The operation of the press must include slow, regular and progressive pressure increases. Indeed this is vital in order to limit the sifting of the retrousses. Manual operation is most suitable for this delicate work but it does require continuous monitoring which is largely incompatible with high production rates

      To resolve this difficulty while continuing to meet the slow and progressive extraction standards obligatory in Champagne, the AVC technical section together with some Champagne professionals and the press manufacturers have defined a reference guide. This book defines the limits on the duration and the pressure that can be exerted on the grapes. This committee then created automatic control panels with the advantage of a built-in memory containing several programmes that the press-worker can employ depending on the grape-variety and maturity.

      There are currently three types of panel that comply with this reference guide:

- 1st Generation panels with pre-established programmes (Manufacturers - Bücher, Coquard, Diemme, Jouglet, Magnum, Mazancourt, Péra, Siprem, Willmes).

      Everything on these panels is pre-defined - the choice of pressure level, optional levels, duration of pressure maintenance and the intensity of retrousses. Initially a programme is chosen which can, depending on the grape quality, be manually modified at any time during the pressing.

- 2nd Generation panels with programmes for juice flow and calculated delays (Manufacturers - Diemme, Jouglet, Péra, Siprem, Willmes).

      The duration of each pressing is automatically linked to the frequency of recapture and to the level of pressure chosen, without manual intervention. There are two time periods pre-defined by the programme - the recapture time and the maximum length of support at a given stage. The intensity of the retrousses is pre-determined.

- 3rd Generation panels with a programme to measure the real rate of juice flow (Manufacturer - Bücher).

      The AVC tested this type of panel during the harvest of 1994. A meter installed downstream from the press measures the real juice flow-rate and deduces the volume of the flow. The software itself determines the length of time each pressure level is maintained, the passage by optional levels at the end of the pressing and the intensity of the retrousses. This panel ensures a high degree of security.

      The aim of pressing is to extract grape juice. The bunches are very fragile and must be handled very delicately.

      The fundamental principle is simple - you need to start by placing a 'marc' of grapes (the capacity of a traditional grape press) by hand in the press-pan (or press loading space). A marc is approximately 4,000kg of whole bunches. These bunches are then spread out using wooden spades. This is an important detail because it is vital that the juice is not in contact with any exogenous material (such as metal) that could possibly modify the taste. Then the trays, blocked with props or metal T-squares, receive a gradual and intermittent pressure, which lets them descend towards the bunches. Finally the juice flows between the press wattles.

* The very first juice (or 'auto-pressing') results from the grapes being naturally pressed or squeezed during loading. It can produce from 100 to 150 litres. It is often eliminated, particularly when it contains dust, mud or the residue of phytosanitary products. Normally this juice is also oxidised from handling during and after picking.

* The first juice (or 'cuvée') is obtained by three successive and intermittent pressings. The first pressing generally collects around 10.25hl in the 'belon' (an enamelled steel or concrete reception vat). To obtain the authorised 20.5hl, the retrousse takes place. This operation consists of pushing the edges of the press-cake (or mass of less crushed grapes) back towards the central part of the vertical press. The edges of the press-cake are obviously located on the periphery and are therefore subject to a lower pressure. This is done using stainless steel spades. In horizontal presses decompressing and rotating the apparatus achieve this process.

Two new pressings (or retrousses) give a complementary quantity of juice (6.15hl and 4.10hl), making up the cuvée.

* After these three pressings, the edges of the press-cake are yet again cut up, crumbled and pushed to the centre of the press. This yields a third juice (or taille) of 5hl.

The quality of a wine results from a combination of sugar, tartaric acid, malic acid and potassium. These elements are found in the pulp, which is separated into three distinct zones:

- the intermediary zone (1), which is rich in sugar and acid,
- the central zone (2), which is rich in tannin and malic acid,
- the peripheral zone (3), which is rich in potassium.

The separated pressing aims to extract the components that are contained in the pulp. Zone 1 bursts first of all, giving the cuvée a different chemical composition to the taille. It is richer in sugar and acid, more balanced and has a stronger bouquet. A cuvee can neither be tinted nor oxidised. The taille is fruitier, less acidic and lightly tinted. The latter occurs because the must contains mineral and colouring material called colloids and albuminoids.

The cuvée and the taille are therefore vinified separately. The concern for quality always overrides that for quantity and is paramount at all stages leading to the production of the sparkling Champagne wine - from the cultivation of the vines to the production of the cuvées.

Once the cuvée and taille are obtained, the rest of the press-cake is placed on a 'séchoir' (dryer), which is a small, hydraulic, and very powerful press designed to extract the 'rebêches' (final pressed juice). This is sent directly to the distillery and provides the alcohol. The wine producer is required to do this by law.w.

Finally, the press residue - the skin, stems and pips (called 'aignes') - are distilled after fermentation to obtain the ‘marc de Champagne’.

      The different juices – the auto-pressing, the cuvée and the taille - are then collected and poured into either oak or cement measuring vats called 'belons'. Under the press spout, a stainless steel sieve collects the solid residue - skins, stems, pips, fragments of earth and cellulose.

To limit the oxidation of the must in contact with the air, the wine-maker carries out the process of sulphiting, whereby a very small quantity of this oenological product is added. This is essential for obtaining a quality must.

The sulphiting also eases the decanting of the juice by ensuring the insolubility, the coagulation and consequently, the natural sedimentation of the deposits from the must. The natural grape pectic enzymes also encourage this reaction.

       After passing through the belons, the must is transferred into 'débourbage' vats. Here it rests for between 8 and 15 hours in order to ensure all foreign materials in suspension can settle.

       This decanting process takes place in two stages:

      . Coagulation phase - the cellulosic (or mucilaginous) material coagulates and gains weight.

       . Sedimentation phase - during which this material (increasingly concentrated) naturally settles as a muddy deposit (the 'bourbes') at the bottom of the vat. It is this deposit that will be eliminated by racking.

      The clearing vats are fitted with flow butterfly valves equipped with decanter turnings. The juice leaves the vats, free of the majority of solid particles, for partitioned tankers that then transport it to the fermentation wine cellar.

      On arrival in the wine cellar, a sample from each tanker partition is taken for a first analytical control. The must is then placed in different fermentation vats - enamelled steel, stainless steel, glassed cement or wooden tuns. At each of these stages, and for each must, the following details are scrupulously adhered to - the type of separation, the grape-variety and the grouping of arrivals according to their origin.