Chapter 2 – Saccharomyces Yeasts II: Secondary Fermentation

Publisher Summary Traditional-method sparkling wines, which are made using particular varieties of grape, contain carbon dioxide gas as a natural consequence of the process used in their production. This gas is a byproduct of the secondary fermentation of natural or added sugars in the base wine. The fermentation takes place in closed vessels and the resulting wine has a minimum pressure of 4 atm at 20oC. Depending on the winemaking method used, sparkling wines are classified as tank-fermented wines or bottle-fermented wines. In the tank-fermented method, secondary fermentation takes place under isobaric conditions in a sealed tank with a capacity of tens of hectoliters. These tanks are equipped with stirring mechanisms that mix the yeast uniformly into the base wine. In the transfer method, the sparkling wine is produced in bottles, which are generally magnums measuring 1.5 or 2 L to minimize storage space requirements. It is then left to age on lees for at least 2 months, after which it is transferred to a tank maintained under isobaric conditions with carbon dioxide or nitrogen to prevent loss of the gas. The wine is then cold processed at –5oC, filtered, and sometimes transferred to a second tank.