The Art of the Second Fermentation in Champagne

5th March 2024

Champagne bottles stored in Epernay

The second fermentation in Champagne transforms a still wine into the world-renowned sparkling wine. This critical phase is not only about creating the bubbles that Champagne is famous for but also about influencing the flavor, aroma, and overall quality of the final product.

The Biochemical Process

At its core, the second fermentation is a biochemical reaction. When the winemaker adds the liqueur de tirage—a mixture of sugar and selected yeasts—to the base wine, it sets the stage for fermentation within the sealed environment of the bottle. The type of yeast used is crucial; it must be able to withstand the high-pressure conditions that develop inside the bottle.

Yeast cells consume the added sugar, breaking it down into ethanol (alcohol), carbon dioxide (CO2), and heat. Unlike in the first fermentation, where CO2 escapes, the sealed bottle traps the gas, dissolving it into the wine under pressure and creating the bubbles that Champagne is celebrated for.

The Formation of Bubbles

The solubility of CO2 in wine is a key factor in the formation of bubbles. Under the high-pressure conditions inside the bottle, more CO2 dissolves into the wine than it would under normal atmospheric pressure. When the bottle is opened and the pressure is released, the solubility decreases, and the CO2 comes out of solution, forming the bubbles that effervesce in the glass.

Autolysis and Flavor Development

An equally important aspect of the second fermentation is the autolysis of yeast cells. After the yeast has consumed all available sugar, the cells die and begin to break down, a process that can last for several months or even years, depending on the winemaker’s goals. During autolysis, the dead yeast cells release compounds into the wine, including amino acids, proteins, enzymes, and nucleotides, contributing to the Champagne’s texture, complexity, and flavors.

These compounds are responsible for the toasty, bready, or biscuity flavors often associated with fine Champagne. The extent and character of these flavors depend on the duration of the lees aging, with longer periods typically resulting in more pronounced autolytic characteristics.

The Role of Pressure

The pressure inside a Champagne bottle reaches about 5 to 6 atmospheres (approximately 75 to 90 pounds per square inch), significantly higher than atmospheric pressure. This high pressure is essential not only for dissolving sufficient CO2 to create the desired level of effervescence but also for influencing the size and quality of the bubbles. Finer, more persistent bubbles are often associated with higher-quality Champagne, a characteristic influenced by the conditions of the second fermentation and the aging on lees.


The second fermentation is an ace of winemaking, where science and tradition converge to create something truly extraordinary. Beyond simply adding bubbles, this process is fundamental to developing the Champagne’s character, influencing everything from the texture and aroma to the flavor profile. It’s a demonstration to the skill and patience of Champagne makers, who arrange this complex biochemical work to produce one of the world’s most celebrated beverages.

Teri Wheeler

Wine Professional from South Australia, has made a mark in the wine industry due to her passion and extensive experience in the industry, as a Wine Ambassador, Business Develop Manager, Merchant Success Manager, Wine Educator, Writer, Examiner and Critic for various wine companies and publications, all underpinned by her soon to be completed Level 4 Diploma in Wines from the Wine & Spirit Education Trust, making her a valuable figure in the world wines.