Effervescence was neither discovered nor invented. It is a natural process produced by yeasts, the micro-organisms that transform grape sugars into alcohol and carbon dioxide by fermentation. Mastering that process has been no mean task, gradually building an expertise that has its roots in the patient observations of 17th Century Champagne makers..
Champagne wines were originally made straight after the harvest, by fermenting the newly pressed grape juice in casks. Due to the cold climate however, fermentation was usually short-lived, leaving the wines with a certain quantity of residual (unfermented) sugar. As a result, fermentation would recommence in spring when the weather warmed up (a process known locally as the ‘la montée de sève’, literally ‘sap rising’). The gas given off in the process caused the wines to ‘bubble’ but could not be contained by the casks. For this reason, the wines were more or less effervescent depending on how cold it was in the winter and when they were actually drunk.
Bottling was introduced in the late 1600s as Champagne makers looked for ways to improve the storage and shipment of their wines. Unlike casks, bottles served to preserve the effervescence that later reappeared in the glass. The change was an immediate success although the effervescence itself remained a very hit-or-miss affair. Champagne makers had yet to grasp the three key concepts that would make all the difference: firstly, blending grapes with good effervescent potential; secondly, bottling the wines in March when the weather turns warmer; and thirdly, using strong bottles fitted with an airtight stopper.
So began 300 years of research and improvement that continues today.
To begin with, effervescence was at the mercy of Nature and just as fickle. The breakthrough came in the 19th Century when scientists discovered new techniques that made effervescence much more predictable. The solution lay in:
Effervescence caused substantial breakage with sometimes as many as half the bottles exploding. The English, who imported the wines in casks for bottling on arrival, were the first to opt for bottles made of thicker glass. Champagne makers followed their example and designed a bottle of their own in 1735. Moulding was introduced in 1882 to standardize capacity, followed by glass blowing using compressed air, which was adopted by the industry in 1918. Today a bottle of Champagne is designed to withstand a pressure of 20 bars or three times the natural pressure in Champagne.
Corking plays a critical role in secondary fermentation (or ‘prise de mousse’). Until 1670, bottles were plugged with a ‘broquelet’, a wooden toggle wrapped in hemp and soaked in tallow. This failed to prevent the gas or wine from leaking, so the introduction of the cork stopper in 1685 was a huge improvement. This new stopper was made from a single lump of natural cork inserted deep into the bottleneck and held in place first by hemp string, then by wire or staples. The next breakthrough came in 1960 when it was decided to retain the cork stopper for the finished product but to use a more practical crown cap for cellared Champagne prior to disgorging.
Around 1820, Champagne makers started to add rock sugar to their cuvees, to kick-start secondary fermentation. Some years later, wine enthusiast and former Châlons-en-Champagne pharmacist, Jean-Baptiste François invented a method to determine the total sugar content in the cuvee. By the late 19th century, scientists had worked out that the addition of 4 grams sugar/litre raised pressure by 1 bar after fermentation.
In spite of this fundamental discovery, for a long time the foaming process was carried out with yeasts from the alcoholic fermentation. But this method was very random.
Despite Pasteur’s key discovery, secondary fermentation continued to rely on the yeasts produced naturally by alcoholic fermentation. As a result the whole business was very unpredictable and it would be some years before winemakers started to achieve more reliable results. This came with the introduction of selected, cultured yeast, prepared as liquid leaven: high-density yeast preparations, cultured first in grape must and then in wine, so as to imprint the yeast cells with the characteristics of the bottled wine that they will eventually inoculate.
Research continued throughout the 20th century to select ever more reliable yeasts and improve the leavens used to inoculate Champagne and kick-start secondary fermentation in bottle.