How Sparkling Wine is Made
Have you ever wondered how they get the bubbles into sparkling wine?
You may have pictured a kind of giant carbonation machine injecting gas into the wine, like you can do at home to make soda water. While this is possible, it’s also the least desirable way to go about it.
Instead, winemakers prefer to harness the carbon dioxide (CO2) that is naturally produced during fermentation.
In most cases, a dry, high-acid, low-alcohol base wine is created first. Then a second round of fermentation is initiated inside a closed vessel, thus trapping the CO2 inside.
There are two main methods for producing sparkling wine: the Traditional Method and the Tank Method. Let’s explore both in more detail.
THE TRADITIONAL METHOD
This method was made famous in the region of Champagne, France, where it is also known as méthode champenoise. It is the most highly regarded method of in-bottle fermentation.
To learn more about Champagne, click here.
In addition to Champagne, it is also used for all English sparkling wines, Spanish Cava, and is referred to in South Africa as méthode cap classique. Several other cool-climate regions around the world make some as well.
Base Wines and Blending
First, base wines are fermented separately. Each grape varietal and different vineyards are kept separate.
This first fermentation generally takes place in stainless steel tanks, although a few producers elect to use old oak barrels for added structure.
Then, the winemaker blends the base wines together to create the desired flavour profile. They may even choose to blend in wines from previous vintages.
Only during exceptional years are single-vintage wines produced in Champagne. These are referred to as “vintage” and the year will be cited on the bottle. Blends of different years are referred to a “non-vintage”.
Blending in this manner is attributed to the great monk Dom Perignon, often referred to as the “inventor of Champagne”.
In the Bottle
The base wines are then bottled. This is the step that sets the Traditional Method apart from the Tank Method, as the second fermentation will take place inside the bottle.
A small mixture of yeast, sugar and wine is added to each blend (“cuvée) to start a second round of fermentation.
It is sealed with either a crown cap (like a beer bottle cap), or a cork that has been clipped in place to keep it from popping open. Then it is left to ferment.
Just like in the first fermentation, the yeast eats the sugar, and creates carbon dioxide. Except, instead of being able to escape into the atmosphere, this time the carbon dioxide becomes trapped, creating natural carbonation.
Once the sugars are gone, the yeasts die off, becoming “lees” that settle to the bottom of the bottle. Over time, these lees will break down in a process called “yeast autolysis”. This is what gives Champagne and other traditional method sparkling wines it’s bready, biscuit aromas (also called “autolytic notes”). The longer the wine spends on the lees, the strong the notes.
Riddling
In preparation for bottling, we need to get rid of those lees. But we don’t want to disturb them too much, or the autolytic notes will become too overwhelming. To avoid this, the bottles go through a process known as “riddling”.
Historically, this was done by hand. The bottles were tediously rotated, a tiny bit at a time, slowly moving from a horizontal to inverted vertical position.
Fortunately, we now have massive machines called “gyropalettes” that automate the process, as they can rotate hundreds of bottles at once. This also speeds up the process significantly, as the bottles can be rotated every 30 minutes, rather than once per day.
Disgorging
When the bottles are fully inverted, the lees settled into the neck of the bottle. The neck is then frozen, creating a plug of ice and lees.
When the crown cap or cork is removed, the pressure of the trapped carbon dioxide forces the plug out of the bottle all at once. A small amount of wine is also lost, but that will be replaced.
Dosage
To replace the wine that was lost, winemakers add a small mixture of wine and sugar back into the bottle. The amount of sugar in the dosage will determine the final level of sweetness in the wine.
“Brut nature” wines have absolutely zero sugar added.
“Brut” wines have only a small amount of sugar added, so that they still taste dry but balance out the high acidity.
“Demi-sec” wines are medium sweet.
Bottling
Finally the wines are resealed with a mushroom-shaped cork and a wire cage. A regular cork and foil aren’t enough to contain the carbon dioxide.
ARTISANAL METHOD AND PET-NAT WINES
The Artisanal Method (méthode artisanale) is a variation of the Traditional Method.
These wines are actually bottled before the FIRST fermentation is complete.
Although good quality wines can be made this way, the process is harder to control, and thus less reliable.
Most of these wines are disgorged, but Pet-Nat wines (Pétillant natural) are the exception. Instead, the yeasts remain in the bottle. The cloudy appearance may be off-putting to a new wine drinker, but they are worth trying at least once!
THE TANK METHOD
The Tank Method of creating sparkling wines goes by many names: Cuve Close, Charmat, and Metodo Italiano for example.
This method is significantly cheaper for winemakers to produce, and enjoyed around the world, making it a very popular option. Great examples are Prosecco and Lambrusco.
The main difference that you as a consumer will notice is the lack of autolytic flavours in the wine. Winemakers tend to gravitate to this method when working with more aromatic grapes and delicate flavours.
Base Wines
Similar to the Traditional Method, we must first create a base wine. Prosecco, for example, begins with a still wine made from Glera grapes.
In the Tank
The key difference between this and the Traditional Method is where the secondary fermentation takes place.
In the Traditional Method, the base wine is bottled right away. But in the Tank Method, secondary fermentation takes place in large pressurized tanks.
The base wine is sealed in a cool-temperature tank along with yeast and sugar, and the magic begins.
Filtration
Because the wine hasn’t been bottled yet, we don’t need to worry about the tedious processes of riddling and disgorging.
Instead, the lees are simply filtered out.
This is why we don’t have the autolytic notes of bread, pastry, and biscuits like we do in the Traditional Method. No lees = no autolysis.
Bottling
Finally, the wine is bottled while still under pressure. Due to the force of the carbon dioxide, a thick mushroom-shaped cork and wire cage are used to seal it until it’s ready to drink.
THE ASTI METHOD
The Asti Method is a variation of the Tank Method that is used specifically for sweeter wines, with similar principles to the Artisanal Method.
This method has become practically synonymous with Moscato wines (Moscato d’Asti).
The juice of the Muscat grapes is placed into a pressurized tank with yeast and begins to ferment. At first, the carbon dioxide is allowed to escape, just like when creating a base wine. But partway through the process, the tank is sealed and the rest of the carbon dioxide becomes trapped inside.
Instead of letting the fermentation process run to conclusion, it is stopped prematurely. This is done by lowering the temperature of the tank to kill off the yeasts before all of the sugar has been consumed.
The yeasts are then filtered out and the wine is bottled. Winemakers must be particularly cautious with this step though. If any yeast is left behind, it can restart the fermentation process inside the bottle, ruining the wine.
When done right, this will result in wines that are sweet, sparkling, and low in alcohol. Moscato is often cited as a favourite of people new to wine. Now you know how it’s made!
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2 years
Tagged Red wine, wine, winemaking