Definition - What does Carbon Dioxide mean?
Carbon dioxide is a by-product of the fermentation process. During fermentation, the sugar in the grape juice is converted to carbon dioxide and ethanol; for still wines, the carbon dioxide is allowed to escape, however, for sparkling wines, the carbon dioxide is trapped and makes wine effervescent.
During fermentation, we know the yeast introduced into the must eats the sugar, converting it to ethanol alcohol, and carbon dioxide is the by-product of this process.
WineFrog explains Carbon Dioxide
For many wines, the carbon dioxide is allowed to escape and doesn’t impact the mouthfeel or taste of the final product. If the fermentation is allowed to vent, the carbon dioxide gas will escape, however, if the fermentation is sealed, it builds up pressure, and the carbon dioxide will be infused with the wine creating effervescence, which is the basis of sparkling wine and Champagne.
That’s the big story of carbon dioxide, however, fermentation is a metabolic process, and carbon dioxide plays an integral role in regulating the yeast metabolism, particularly the growth of the yeast. How much and how quickly carbon dioxide is produced depends on the overall levels of sugar and the types of sugars present in the wine. Carbon dioxide is produced faster in the presence of glucose, followed by sucrose and fructose. Understanding how the yeast metabolize sugars is key for vintners in order to be able to stop the fermentation to produce a specific style of wine.