Lees ageing
In many cases the wine is stored on the lees under carbon dioxide pressure for a long time before disgorging, to get a more mature character. The requirement for non-vintage Champagne is at least 15 months of storage on the lees, and for vintage Champagne at least three years.
Yeast autolysis releases amino compounds, including peptides, proteins and enzymes, as well as lipids and volatile aromatic compounds, into the wine. The volatile compounds, proteins, peptides and amino acids released by autolysis become available for Maillard reactions. Maillard reaction products, including furans, acrylamides and nitrogen, sulfur and oxygen heterocycles, have been identified in aged sparkling wines. Strecker degradation products 2-methylpropanal, 2-methylbutanal, methional and phenylacetaldehyde have been identified in aged sparkling wines produced from Chardonnay and Pinot noir.
During and after the second fermentation the wine is stored horizontally in contact with the yeast cells, for a period ranging from 9 months to several years. Some amino acids are precursors of aroma compounds, some peptides and proteins taste sweet or bitter and can influence foam stability, and mannoproteins contribute to the body of the wine.
Sparkling wines are produced and aged at a low temperature (15 ± 3°C), at a pH of 3 to 4, under a pressure of 6 atm, with a titratable acidity of 7 to 12 g/l and 12% ethanol by volume.
Flavour compounds formed in the bottle
Several Strecker degradation products (thiazole, 2-acetylthiazole, trimethyloxazole, 2-furanmethanethiol and thiophene-2-thiol) have been identified in model wine conditions, which suggests that Strecker degradation is reduced but not inhibited in wine. All five have low sensory perception thresholds, at microgram-per-litre level, and odour activity values above 1, which indicates that they are likely to matter to sparkling wine flavour. In Champagne wines the level of thiophene-2-thiol correlates with cysteine; at 1 μg/L it lies above its detection threshold in water of about 0.8 μg/L.
The Strecker products 2-methylpropanal, 2-methylbutanal, methional and phenylacetaldehyde were monitored at 6, 12 and 24 months of bottle ageing. Their highest levels were found at 24 months, when all concentrations exceeded the reported odour thresholds.
Effervescence and terminology
Carbon dioxide trapped during the second fermentation gives the wine its effervescent character, at post-fermentation pressures of approximately 6 atm. Champagne in bottles of 375 ml, 750 ml and 1.5 liters must be produced with the traditional method. In Europe the term méthode champenoise was outlawed in 1994 for all wines other than Champagne.
Smaller and larger bottles are usually produced with the transfer method. On labels the traditional method may be called méthode traditionnelle, méthode classique, traditional method, classic method, or the ambiguous term bottle fermented.
In 2021 Russia banned the designation шампанское for imported sparkling wine, including sparkling wine from the Champagne wine region, and reserved it for domestically produced sparkling wine. The name is still used for some sparkling wines from former Soviet republics, such as Sovetskoye Shampanskoye and Rossiyskoe Shampanskoe.
Origins of the method
Christopher Merret presented a paper at the Royal Society in 1662 that detailed what is now called méthode traditionnelle. His work coincided with technical developments by English glass-makers, who could produce bottles able to withstand the internal pressures of the second fermentation.
The second fermentation is induced by adding several grams of the yeast Saccharomyces cerevisiae and rock sugar to the bottle, and each producer has its own secret recipe.
