carbon dioxide

from

A colorless, odorless, incombustible gas. Carbon dioxide (CO₂) is one of the two by-products of FERMENTATION, the other being ALCOHOL. Yeast acts on the natural grape sugar and converts 40 to 45 percent of it to carbon dioxide, which in most cases escapes into the air. In the production of SPARKLING WINES, however, carbon dioxide is purposely trapped in the wine to create effervescence.