Chaptalisation
Before primary fermentation begins the must maybe enriched using a sucrose solution made from sugar cane or beetroot. Enrichment is carried out to aid primary fermentation to achieve an alcohol content of 10.5°-11.5°. This sugar enrichment is called chaptalisation. If the weather in a particular year was hot and sunny and the grapes were full of sugar at harvest, then chaptalisation may not be necessary.
Primary Fermentation
The oenological laboratory of the Comité Champagne (CIVC) provides a strain of yeast called Saccharomyces cerevisiae to all producers. Inoculated yeasts are added to the must and primary fermentation begins inside the steel tanks. Over the years though, many champagne houses have actually developed their own special strains of yeast.
The yeast consumes the must’s natural grape sugars (Glucose and Fructose), and converts about 95% of it into; alcohol, CO2 and heat as well as 5% waste products like lactic acid all of which play an important role in imparting sensory characteristics to the developing wine.
Today, fermentation is mostly carried out in special steel tanks. It is important to counteract the heat generated in primary fermentation so a chilled liquid (usually water) is run around the surface of the tank to ensure fermentation is carried out at a controlled temperature of 16 – 20°C.
C6 H12 O6 + yeast ——-> 2 C2 H5 OH + 2 CO2 + Heat + Waste Products
In the Champagne appellation the must becomes classed as base wine when it has achieved an alcohol level of 7% by volume or 7.5°. Primary fermentation usually takes around 2 weeks to complete.
Malolactic Fermentation
Once primary fermentation has completed, some producers chose to carry out an additional stage of fermentation called malolactic fermentation, or ‘malo’ for short. It is not mandatory to carry out malo as there are both strengths and weaknesses in malolactic fermentation, for example, the Grande Marque Lanson does not use malo. Whether it is performed or not really depends on what flavour and aroma profile the producer is trying to achieve in the finished champagne.
Malo softens the wine, lowering the acidity and improving the base wine’s finesse making it more ‘buttery’. Producers avoid malo if they want to retain the wine’s freshness and fruity aromas. One of the main reason’s producers avoid malo is that the champagnes produced without malo have much greater aging potential. As a result, it would be unlikely for a champagne selected as vintage to go through malo.
2(COOH) – CH3 – CHOH ——-> CO2 + CH3 – CHOH – COOH
Wines going through malo are inoculated with a special type of yeast called lyophilized bacteria. The wine is kept at 18 – 20°C. The whole malo fermentation stage generally takes 4 – 6 weeks. After completion the wine is cooled to 10 – 12°C
Clarification of fermented base wine
During the fermentation process sediment such as dead yeasts settle to the bottom of the fermentation tank. These sediments are called lees.
After fermentation, the base wine needs to be tested to ensure that it does not oxidize. To do this the winemaker exposes the base wine to the air for about 48 hours. If the base wine oxidizes it will turn brown.
After oxidation testing, the winemaker makes an initial tasting assessment. The winemaker then needs to separate the base wine from the lees. This process is called racking and involves siphoning-off the base wine from the lees into clean tanks. Racking ensures that potentially bad flavors from the decomposing yeast are not passed to the base wine.
In the lifecycle of champagne production, the racking process usually takes place at the end of the year e.g. October – December.
After racking the base wine is still quite cloudy and it needs further clarification to ensure the final base wine is clear. There are 3 main methods of clarification:
Fining
This is the oldest technique and often involves the addition of a clay like bentonite or an animal protein like egg white. The function of fining agents is to bind with unwanted larger compounds e.g. tannin, to form a colloid. Colloids are large enough enable them to be filtered out of the base wine. Fining usually takes between 10 – 14 days to complete. Not all winemakers use fining, for example, use of an animal protein obviously makes the champagne non-vegan.
Filtering
Fined base wine must be filtered to remove the unwanted colloids formed during fining. Some winemakers filter their base wines but don’t fine them. The winemaker will carefully chose the medium used to filter the base wine. The winemaker always tries to balance the removal of unwanted material while trying to maintain the individual characteristics of the base wine.
Centrifuging
Special centrifuges can be used that significantly help with the clarification of base wines. Centrifuging significantly speeds up clarification, however the machines are expensive and not many smaller RM can afford to buy the equipment. Base wines can be spun at 5 – 15,000G depending on the machine used.
Each base wine is then individually stored according to vineyard and grape variety. After clarification, the base wine is now ready for the next stage of the process, the oenological masterpiece of blending the base wines.