Before we get into how sparkling wines are made, we should first make a distinction between sparkling wine and champagne. Champagne is sparkling wine, but sparkling wine is not necessarily champagne. True champagne is produced in the Champagne region of France by using the Methode Champenoise and is produced from a high quality grape. In many circles in the United States, the term "champagne" has become a general term to include any sparkling wine. These are frequently made from inferior grapes through bulk processing and are often sweetened to mask their inferior quality. They are not true Champagnes.
Sparkling wines are made from both white and red grape varieties. The quality of the fruit is critical to the outcome of the finished product. In the Champagne region of France, Chardonnay, Pinot Noir or Pinot Meunier are used. But in other internationally recognized sparkling regions, like Asti, other varieties such as Muscat Blanco may be used. The grapes are harvested earlier than those picked for still (table) wine. There are several reasons for this early harvesting. One reason is to obtain a lower alcohol level in the cuvee (wine made from the initial fermentation, also called "base" wine). During the fermenting process the sugar is converted to alcohol, therefore the lower the sugar content of the grapes, the lower the alcohol content of the finished product. The reason for the lower alcohol content in the base wine is that the wine will go through another fermentation process that will increase the alcohol level. Another reason for harvesting grapes while at a lower sugar level is to produce a higher total acidity and lower pH rating. This adds longevity and crispness to the wine.
Now lets take a look at the three different methods vintners may use to make sparkling wines. Methode Champenoise is a more labor-intensive and expensive method than the other two methods of producing sparkling wine. After harvesting the fruit, the juice is pressed and put into containers for the first fermentation. These containers are either stainless steel vats or oak barrels. When the first fermentation is complete, various lots of wine are blended together to produce an assemblage (the final blend of varieties for the finished wine). Then a mixture of yeast and sugar, called a triage, is added to the base wine. The wine is bottled with a small plastic cup that fits in the neck of the bottle and collects any sediment. This small plastic cup is called a "bidule" The second fermentation takes place in the bottle and due to the sugar and yeast being added, alcohol and carbon dioxide are produced. Due to carbon dioxide formation and pressures up to 90 pounds per square inch, bottles for Champagne and sparkling wine must be thicker than regular wine bottles. During the second fermentation, temperature plays an important role. Cooler temperatures produce finer bubbles. Once the second fermentation is complete, dead yeast cells begin to break down and form a sediment in the wine. This process is called autolysis. The winemaker decides how long to allow for the autolysis process and this in turn has an impact on the final taste of the wine. The sediment must then be removed without losing the carbon dioxide and sparkle. The first step in doing this is riddling or remuage. In years past, this was done by inserting the neck of the wine bottle into a rack, called a pupitres, that would hold it at a 45 degree angle so the dead yeast cells would settle into the neck where the bidule was attached. Then every few days, a trained person, called a remuer, would give each of the bottles a quick shake and increase the angle of the bottles until they were eventually positioned completely downward, thereby collecting all the sediment in the neck. Today, the riddling process is automated. Next the sediment is removed by disgorgement. This is where the bottle is placed neck down in an icy brine to freeze the sediment into a solid plug. The cap is then removed and the pressure inside the bottle causes the frozen sediment to be expelled. Then a "dosage" is added. This dosage is a small amount of wine mixed with sugar and sometime brandy and it determines the sweetness or dryness of the sparkling wine. The bottle is then corked and secured with a wire hood.
The Transfer Method of making sparkling wine is similar to the Methode Champenoise except that instead of riddling to remove the sediment, the wine is transferred to a pressurized tank where the sediment is filtered. It is then bottled, corked and secured with a wire hood in preparation for sale to the public.
The Charmat Bulk Process is the quickest and least expensive method of making sparkling wine. With this process, instead of the wine going through the second fermentation in the bottle, the base wine is placed in a temperature-controlled, pressurized tank to which sugar and yeast is added. The secondary fermentation takes place in this tank without the release of any carbon dioxide. This tank acts like a very large bottle. Once the fermenting is complete, the wine is filtered under counter pressure and bottled using a counter-pressure filler. Because the wine has not spent the same amount of time in contact with the carbon dioxide, the bubbles tend to be larger and dissipate more quickly.
Marcia Parks is a wine reviewer and publisher of a wine review web site. To read reviews and learn more about wine visit http://www.wine-reviewer.com