Sparkling wine, fizz, bubbly: call it what you will, but its effervescence spells joy and celebration. These tiny bubbles make all the difference, but how do they get there? How different sparkling wines are made can help you choose the right wine for the right occasion.
First things first: bubbles form when carbon dioxide gas dissolved in wine is released. Most sparkling wine bottles are thus under pressure, which explains the traditional spago (thread) closure for slightly sparkling Prosecco, and the wire muselet for fully sparkling wine. Both keep the cork in place.
Pressure is also why sparkling wine bottles are heavier and thicker than traditional wine bottles and have a deep punt in their bottom. Fully sparkling wine has up to six atmospheres of pressure, so bottles need to be structurally sound and sturdy. As the bottle is opened, that pressure releases and the wine begins to sparkle.
So how does carbon dioxide get into wine? Broadly speaking, there are three ways. The first way is to add it, like in soda. The second method is to trap carbon dioxide from the wine’s initial fermentation. The final way is to put finished wine, known as base wine, through a second fermentation and trap the resulting carbon dioxide. This can happen either in a tank or bottle, and it’s the way most sparkling wine is made. But let’s discuss the first two methods.
Adding carbon dioxide creates the least persistent effervescence, as the wines are just slightly fizzy. A special closure is not necessary.
It’s also possible to make a fizzy wine by trapping carbon dioxide from the first alcoholic fermentation. Usually, such carbon dioxide is allowed to escape, but a pressurized tank traps the gas at a desired point to create a fizzy wine.
Depending on when this process is halted, there can be residual sweetness in the wine. It’s then filtered to prevent further ferment and bottled under pressure, which preserves natural sweetness and fruity flavor. The resulting fizz is lively and frothy. This is how Asti Spumante is made.
Trapping carbon dioxide inside a bottle is known as méthode ancestrale, where a wine with residual sweetness is bottled and continues to ferment until all sugar is consumed. Trendy pétillants naturels, or pét nats, are made in this manner.
But now on to getting bubbles into wine via second fermentation. There’s a huge distinction between secondary fermentation in tank, known as Charmat method, and secondary fermentation in bottle, known as traditional method, méthode traditionnelle or metodo classico. Both create sparkling wine, but they produce different character and virtues. Both of these methods start out with still, dry base wine, to which an exact amount of both sugar and yeast is added which will induce the second fermentation.
For the Charmat method, a base wine that’s augmented with sugar and yeast is put into a pressurized tank where the second fermentation takes place. The carbon dioxide is trapped, and the dead yeast cells sink to the bottom. While these dead yeast cells (known as lees) add a degree of flavor, there’s little interaction between lees and wine. The resulting bubbles are bigger and frothier, and the flavors are far less complex. After a few months on lees, the wine is filtered and bottled under pressure.
This method is easier, cheaper and faster than the traditional method. The base wine’s primary varietal flavors remain and are accentuated by the lively, frothy foam. This is how most Prosecco is made, where the floral, fruity notes of the Glera grape take center stage. Stefano Ferrante, chief winemaker at Prosecco Zonin1821 says, “This way, we can obtain freshness and aroma without the excessive structure and secondary aromas given by yeast contact.”