Most sparkling wines go through two fermentations: one to turn the grape juice into still wine without bubbles (that’s called a base wine) and a subsequent one to turn the base wine into bubbly wine. The winemaker instigates the second fermentation by adding yeasts and sugar to the base wine. The added yeasts convert the added sugar into alcohol and carbon dioxide (CO2) bubbles.
When yeasts convert sugar into alcohol, carbon dioxide is a natural by-product. If fermentation takes place in a closed container, that prevents this carbon dioxide from escaping into the air. With nowhere else to go, the CO2 becomes trapped in the wine in the form of bubbles.
Beginning with the second fermentation, the longer and slower the winemaking process, the more complex and expensive the sparkling wine will be. Some sparkling wines are ten years in the making; others are produced in only a few months. The slow-route wines can cost more than $100 a bottle, while bubblies at the opposite end of the spectrum can sell for as little as $4.
Although many variations exist, most sparkling wines are produced in one of two ways: through second fermentation in a tank, or through second fermentation in a bottle.
Tank fermentation
The quickest, most efficient way of making a sparkling wine involves conducting the second fermentation in large, closed, pressurized tanks. This method is called the bulk method, tank method, cuve close (meaning closed tank in French), or charmat method (after a Frenchman named Eugene Charmat, who championed this process).
Sparkling wines made in the charmat (pronounced shar mah) method are usually the least expensive. That’s because they’re usually made in large quantities and they’re ready for sale soon after harvest. The whole process can take just a few weeks. Also, the grapes used in making sparkling wine by the charmat method (Chenin Blanc, for example) are usually far less expensive than the Pinot Noir and Chardonnay typically used in the traditional or champagne method.
Bottle fermentation
The more traditional method of producing sparkling wines is to conduct the second fermentation in the individual bottles in which the wine is later sold. The technique of conducting the second fermentation in the bottle is called the classic or traditional method in Europe; in the United States, it’s called the champagne method or méthode champenoise.
Champagne has been made in this way for over 300 years and, according to French regulations, can be made in no other way. Many other French sparkling wines produced outside of the Champagne region use the same process but are allowed to use the term crémant in their names rather than champagne.
Bottle fermentation is an elaborate process in which every single bottle becomes an individual fermentation tank, so to speak. Including the aging time at the winery before the wine is sold, this process requires a minimum of fifteen months and usually takes three years or more. Invariably, bottle-fermented sparkling wines are more expensive than tank-fermented bubblies.
Taste: The proof of the pudding
The two different methods of producing sparkling wines result in different tastes:
Tank-fermented sparklers tend to be fruitier than traditional-method sparkling wines. This difference occurs because in tank fermentation, the route from grape to wine is shorter and more direct than in bottle fermentation. Some winemakers use the charmat, or tank, method because their goal is a fresh and fruity sparkling wine. Asti, Italy’s most famous sparkling wine, is a perfect example. You should drink charmat-method sparklers young, when their fruitiness is at its max.
Bottle fermentation makes wines that tend to be less fruity than charmat-method wines. Chemical changes that take place as the wine develops diminish the fruitiness of the wine and contribute aromas and flavors such as toastiness, nuttiness, caramel, and yeastiness. The texture of the wine can also change, becoming smooth and creamy. The bubbles tend to be tinier, and they feel less aggressive in your mouth than the bubbles of tank-fermented wines.