The vital stage in the making of a Grand Marque Champagne is blending – the combination of individual wines to perpetuate a certain taste and style that the consumer looks for in their preferred brand. Think of a blended wine as a grand orchestra in which each soloist contributes their particular talents to create a harmonious whole. Pursuing this metaphor, the soloist’s first task is to prove themselves an accomplished artist in their own right. It is the same for the musts from each plot, which have from the end of the harvest until December to prove their worth. In the course of this time, the different pressing juices (cuvee and taille) must evolve to the point where they are ready for blending. The winemakers meanwhile keep a close eye on how the process develops.
Prior to fermentation, the must may be enriched with sucrose (extracted from beetroot or sugar cane) to increase the alcohol content of the finished wine – a process known as chaptalisation.
By the end of fermentation, the wine should have an alcohol content anywhere between 10.5o and 11.5o. This will increase by 1.2o to 1.3o in the course of secondary fermentation, making for a maximum alcohol content at the point of sale of 13o – which is the legal ceiling imposed on Champagne. Reaching that level is nonetheless essential to bring out the secondary aromas of fermentation.
In especially sunny years, when the grapes are packed with sugar, chaptalisation may not be necessary.
2) Managing natural acidity
The acids naturally present in the grape juice must also be adjusted to enhance aging potential and safeguard freshness in the finished wine. One way of achieving this goal is to induce malolactic fermentation (MLF), an entirely natural process that transforms malic acid into lactic acid.
3) Yeast addition
The native yeasts present on grape skins are not sufficient on their own to conserve the quality and character of each wine. You need a predominance of yeast strains that actively contribute to the fermentation process. Hence the addition of cultured yeasts to the must – special strains selected from natural yeast populations.
One example is Saccharomyces cerevisiae, a yeast strain selected by the CIVC technical department and made available to all by Laboratoires Œnologiques. Commonly known as "baker’s yeast", the rehydrated culture may be added directly to the must at a rate of 10-20 g/hl; or it may first be mixed with a reserve wine. Many Grandes Marques and Champagne Houses cultivate their own selected strains of yeast.
As we can see, this first, delicate, stage of winemaking depends on two entirely natural processes.
The first is the organic process of alcoholic fermentation produced by the conversion of sugar to alcohol; the second is the physicochemical process involved in the clarification of the newly-fermented wine.
What they produce in the end is a still, white, non-effervescent Champagne wine that can be sold under the label "Coteaux Champenois".
Now, let us look in more detail at these two processes.
Alcoholic fermentation has been practised since Antiquity but it has only been clearly understood since the middle of the 19th Century when Louis Pasteur discovered the role of micro-organisms in fermentation. Pasteur was the first to show that fermentation was not caused by exposing sugar to air but by naturally occurring airborne yeasts. So let us examine more closely how this process works.
Yeasts contain enzymes that break down natural sugars (glucose and fructose) and added sugars alike, producing ethanol and carbon dioxide as waste products. The chemical reaction that occurs in fermentation is entirely natural. It usually continues for about two weeks and generates a lot of heat.
In 1815, Louis-Joseph Gay-Lussac devised the following equation: "One molecule of sugar gives two molecules of ethyl alcohol and two molecules of carbon dioxide, as well as a strong emission of heat r".
When applied to wine, this can be expressed by the following chemical formula:
C6 H12 O6 + yeast ---------> 2 C2 H5 OH + 2 CO2 + Q
In1860, Pasteur demonstrated that this chemical reaction only transformed some 95% of the sugar in wine, the remaining 5% being broken down into waste products such as glycerol, superior alcohols and esters, lactic, acetic and succinic acid .
Up until relatively recently, must fermentation was conducted in wooden containers (barrels or vats) or in tanks made of either glass fiber reinforced concrete or enamelled steel. These days temperature-controlled stainless steel tanks with a capacity of 50-1,000hl have largely become the standard for winemaking.
Fermentation starts with a vigorous bubbling - a boiling effect described by French winemakers as the bouillage, usually lasting about five or six days. This is caused by the release of thousands of tiny carbon dioxide bubbles, which rise up through the liquor taking any solid matter with them, producing a frothy mousse that collects at the surface of the must. Hence the need to leave enough space in the tank at the outset.
To control the heat generated by fermentation, the winemaker will often run a refrigerated liquid over the surface of the tank. The aim is to maintain a constant temperature of 16-20°C, encouraging a steady rate of fermentation and reducing loss of aroma through evaporation. The process is complete when the last grams of sugar have been transformed into alcohol and a still wine has been produced. The barrel is then topped up with the same wine to refill the ullage or headspace in the barrel.
Fermentation temperature and the relative density of the mass are monitored on a daily basis, together with the level of CO2 released.
The must becomes wine when the alcohol content has reached 7% by volume, or 7.5% for Champagne AOC wine.
At the end of alcoholic fermentation the wines are left to settle on their lees awaiting MLF (see below) or racking and fining.
Malolactic fermentation has been common practice in Champagne since the ’fifties, which was about the same time as winemakers switched to stainless steel fermentation tanks. Malo, as it is known for short, is carried out by malolactic bacteria that consume the malic acid in wine, producing lactic acid and CO2.
MLF deacidifies wine through the decarboxylation of malic acid to latic acid: the transformation of a di-acid, or molecule with two acidic functions, to a mono-acid with only one acidic function. Since lactic acid is much milder than malic acid, MLF deacidifies the wine. The process can be summarized by the following equation:
(COOH)² - CH2 - CHOH --------> CO2 + CH3 - CHOH - COOH
For many years the mechanics of MLF were poorly understood. It was known to start after alcoholic fermentation, then stop when the weather turned cold in winter before resuming in the spring as temperatures rose. Wine that was already bottled would start to sparkle, an effect believed to be due to the wine reacting in sympathy with the sap rising in the vines .
Winemakers these days have a pretty good grasp of MLF. They understand the importance of maintaining the newly fermented wine at 18-20° C. They may also inoculate for MLF using lyophilized Oenococcus oeni bacteria.
MLF is less spectacular than alcoholic fermentation but takes about twice the time - four to six weeks from start to finish. What is produced is a softer-tasting wine that has lost its acidic edge but gained in finesse. MLF also has a big effect on the longterm stability of wine.
Wines that retain their malic acid, on the other hand, are typically crisper, sharper and more fruit-driven. They are also remarkably long-lived, which explains why some Houses prefer not to put their wines through MLF.
Once alcoholic fermentation and MLF (where applicable) are complete, the wine is gradually cooled to 10-12°C. The next step is to clarify the wine.
In the course of fermentation, dead yeast cells and other sediment (the lees) precipitate out of the must and settle at the bottom of the tank.
As a first step, the wine must be exposed to the air for 48 hours to check that it does not oxidize or turn brown. Next comes a preliminary tasting, looking for any faults or defects and assessing the colour. If nothing untoward is found, the wine undergoes a first racking in the period November-December to separate the new wine from the lees, which are distilled to make Fine Champagne Cognac.
This first racking leaves the wine cloudy due to a high level of suspended solids. Hence the need to clarify the wine using one or more of the techniques described below.
This very ancient technique dates back to Roman times and involves the addition of natural, protein-based fining agents that flocculate on contact with the tannin in the wine. They then sink to the bottom of the tank, taking any solid matter with them – a process that usually takes about 10-15 days.
Filtration takes over where fining leaves off or may be used instead in its place. The wine is passed through a porous medium that retains undesirable particles by filtration-absorption. It is for the winemaker to choose the filtering medium always looking to intervene as little as possible to let the wine speak for itself.
Centrifugal force may be used to accelerate the precipitation of suspended matter, using machines specifically programmed to stabilize the clarity of the wine. Conventional centrifuges produce 5,000-8,000 G of centrifugal force – 14,000-15,000 G for high performance machines – achieving maximum results in minimum time.
Filtration and centrifugation speed up some of the key stages in modern winemaking but require substantial capital investment in plant and equipment.
The wine is by now sufficiently developed to embark on the next stage in its evolution.This is the point that the soloists have been waiting for: the moment that marks the beginning of Champagne-making proper. While production may center on the grapes from a single vineyard, most Champagne wines are a blend of several wines from different growths, grape varieties and vintages. It is the fusion of all these wines that ensures consistency of flavour from year to year. This task falls to the master blender who, like an orchestra conductor, must unite many different voices in a single and perfect harmony.