Carbonic gas

Carbonic gas meaning in winemaking

Carbonic gas, also known as carbon dioxide (CO2), is a natural byproduct of alcoholic fermentation created when yeast cells metabolize sugar molecules. During this process, yeast converts approximately equal parts of sugar into ethyl alcohol and carbonic gas through the chemical equation C6H12O6 → 2C2H5OH + 2CO2. In standard wine production, most of this gas escapes into the atmosphere as fermentation progresses in open or semi-open vessels. However, a small portion remains dissolved in the wine as carbonic acid, contributing to the wine’s overall acidity and pH balance. When fermentation occurs in closed containers—such as sealed bottles during the méthode champenoise or tank fermentation for sparkling wines—the carbonic gas becomes trapped and dissolves under pressure into the liquid. Upon opening, this dissolved CO2 is released, creating the characteristic bubbles and effervescence of sparkling wines. The amount of dissolved carbonic gas determines the wine’s level of sparkle, with fully sparkling wines containing approximately 6 atmospheres of pressure. This natural process is fundamental to producing Champagne, Cava, Prosecco, and other sparkling wine styles worldwide, making carbonic gas essential to both still and sparkling wine production.