Sparkling wines are often classified by the production method that creates the bubbles. Many examples start out as still wines that undergo a secondary fermentation, which may occur in the bottle, following the traditional method employed by Champagne producers, or in tanks under pressure, the Charmat method, which is used to make Prosecco and Asti Spumante. A hybrid approach also exists: the transfer method sees bottle fermented sparkling wines poured into a pressurized tank for ease of filtration and bottling.
Because tank fermented bubbly is a cheaper method of production, less expensive wines with fresh and fruity characteristics can be created. But a new study from the University of Rio Grande in Brazil states that secondary fermentation produces the same wines whether they are produced using the traditional method, in bottles, or in closed tanks. The differences in character come because of the grape varieties used for the base wine and the length of time the wine ages in contact with the dead yeast cells (called lees) that created the second fermentation.
The researchers worked with a base wine made from chardonnay, riesling and pinot noir from the Chandon winery in Garibaldi, Brazil, which is affiliated with Moët & Chandon, which also operates wineries in Argentina, California, Australia, China and India. That base wine was cold stabilised and filtered before being inoculated with yeast and 22 g/litre of sucrose and transferred to 750-milliletre bottles or a vertical 500-hectolitre tank kept under pressure and equipped with a rotary shaker to help keep the lees in suspension, producing a more homogenous wine.
Fermentation lasted eleven weeks. The wines were then left on the lees for 22 months before the final bottling. Three months later, a series of tastings were conducted. The first trials asked trained tasters to distinguish the two methods through 369 triangular tests, which are commonly used to determine if there is a sensory difference between two products. Tasters are presented with one different and two alike samples and asked to identify the unique example. More than half of them got it wrong.
The next stage had 12 judges rate the colour intensity, aroma and flavour intensity of the wines. The conclusion was there were no statistical differences between the sparkling wines: “The method used to perform the second fermentation does not define the quality of the sparkling wines,” they explained.
Producers who use the Charmat method typically look to craft fresh and fruity styles of sparkling wine by selecting aromatic and flavourful grape varieties such as muscat, glera or riesling and limiting the time spent on lees to six months or less to make the flavours of the grape the focal point. Longer contact with the lees can release yeast compounds that contribute bready, toasty and nutty flavours to the finished wine. Maturation in contact with the lees can take months or years for winemakers using the traditional method. For instance, Veuve Clicquot ages its popular brut for more than 30 months, with the vintage and flagship La Grande Dame being aged from five to 10 years.
Some wine lovers might prefer a toasty, refreshing and more expensive Champagne made with the traditional method, while others might favour a charmingly fruity and fragrant Prosecco made in a reinforced stainless-steel tank. Embracing one style over another is a matter of personal preference.