What's Behind the Bubbles?
There’s something mystifying about watching the bubbles appear in a glass of sparkling wine; how they form at the bottom of a glass for what feels like an eternity. In a parallel universe, perhaps they are created by sparkling wine fairies, or unicorn dust. However, here on Planet Earth, there is a simple equation that explains their creation.
Yeast + glucose (sugar: “food”) = ethanol (alcohol) and CO2
CO2 trapped under pressure = absorbed by the liquid = sparkling wine
As fermentation releases CO2 as a by-product, if it does so within a bottle of wine, typically sealed under a crown cap, the CO2 is trapped and has nowhere to escape to, and so it is dissolved into the wine when the pressure in the bottle increases. In turn, the pressure creates bubbles. Magic!
Who discovered this first, or was it all simply an accident?
A mistake on British docks?
Some claim that Champagne’s roots lie in a mistake; in the 1600s it's possible that the Brits left inexpensive still wine imported from the Benedectine monks out on the docks. As there was some sugar left in the bottles, (the wine was slightly sweet), when the wine warmed up it would have continued its fermentation, releasing bubbles. The wines, however, weren't yet imported in bottle format, so either this would have happened in an imported barrel, or it would have occurred once the wine was bottled on UK soil.
The mystery of Dom Pérignon: was he actually tasting stars? … Cute but Unlikely
The "legend" goes that the monk Dom Pérignon not only invented/discovered Champagne, but that he exclaimed, “Come quickly! I am tasting stars!” — However, while it is documented that he worked to improve wine quality, it is likely that the suggestions of him inventing Champagne were much exaggerated to gain prestige for the Abbey of Hautvillers, and this tasting stars quote simply came from early advertising.
British Scientist Christopher Merrett
“Our wine coopers of later times use vast quantities of sugar and molasses to make all sorts of wines, to make them drink brisk and sparkling, and to give them spirits and to also mend their bad tastes,” - Some observations concerning the ordering of wines, Merrett, 1662…
Was British Dr Merrett the first to make the connection between the addition of sugar to create a secondary fermentation, resulting in bubbles?
Blanquette de Limoux: an obscure sparkling wine that was the world’s first?
The first mention of a sparkling wine from Limoux was in fact found in records dating back to 1531, kept by the Benedictine monks of the Saint Hilaire Abbey. So was sparkling wine in fact born in this little corner of southern France?
We may never know, and therein lies the wonder and the mystery of wine with bubbles. Today, there are many ways to create sparkling wines, born from century-long honed methods and innovative new experiments; very rarely from accidents.
The “traditional method,” also known as the “Champagne method,” is a refined (and still developing) way of making sparkling wine in regions all around the world. Work begins in the vineyard; depending on the region and the climate there are many practices that can be adapted to better suit grapes for sparkling wine production. Pressing tends to be gentle, and often using whole bunches to further soften any extraction; stems work like little ridges to allow juice to flow freely.
The wine is then fermented, as if it were a regular white wine, after which it will be aged and/or blended, depending on the producer and style in question. A key decision here for the winemaker is also whether or not to allow the wine to go through malolactic fermentation, the process the malic acid (like the acid in apples) is converted into lactic acid (like the acid in milk), which softens the wine. This wine, known as the base wine, is then bottled.
After a period of time defined by the winemaker, a process called tirage takes place; the process in which sugar, yeast, nutrients, honey or grape must (known as the tirage liqueur) can be added to a wine in order to give the first wine “food” for a second fermentation. When the liquid inside the bottle begins to referment, bubbles are created; the CO2 created by the fermentation has nowhere to escape to and so it is dissolved into the wine in the bottle. This process is slow and can take several weeks.
The wine is then aged (again), and eventually riddled. Riddling is the process by which the bottle is turned extremely slowly so that eventually the bottle ends up upside down. The slow turning allows for the yeast to slide down to the neck of the bottle. It can be done traditionally - by hand - or by using modern machines.
Once upside down, either by freezing the bottle neck and removing the frozen yeast by hand or machine (it simply pops out), or “à la volée;” always by hand, which according to some producers is less invasive to the final quality of the wine. The latter takes a fair bit of skill!
Finally, the winemaker chooses whether or not to add “dosage;” a mixture of sugar and wine). The final sugar level is indicated on the bottle and the terminology depends on the region. Brut is perhaps the most commonly seen; here, winemakers can add up to 12g/L of sugar.
There is a growing movement of winemakers striving to achieve sparkling wines with no addition of sugar whatsoever. This work starts in the vineyard, and if the winemaker feels that their wine has an inherent natural acid/fruit balance, they may choose to simply let the wine be. This is most commonly known as Zero Dosage, or Brut Nature.
A la volée
Pét-Nat & Méthode Ancestrale
Once deemed a fairly peculiar, old-school technique, the Méthode Ancestrale has become one of the great wine successes in recent years.
Today, it is created across the world by many winemakers with experimental souls, who wish to create wine with bubbles by using natural methods. It is often known as pét-nat, short for pétillant naturel (French for naturally sparkling). It is likely the first sparkling wines were made in this manner by accident. When a small amount of yet-to-be fermented grape juice remains in the bottle (ie. the wine has not entirely finished its fermentation yet), if the wine is bottled under crown cap at the correct sugar amount, the wine will become sparkling on its own.
Claus Preisinger, winemaker in the Burgenland, Austria, is a big pét-nat fan. He muses,
“I love to make pétnat - so much that I now make four different types. The idea of bottling fermenting juice means you’re out of the game already at fermentation and you can't influence it anymore. It makes a super interesting wine."
Sounds simple, right? Wrong. Defining the percentage of residual sugar required (% of unfermented grape juice) to create enough bubbles without exploding bottles is immensely complicated. As such, many winemakers disgorge their wines before letting them out onto the market to ensure that bottles don’t smash. If the pressure is just slightly off, and a single bottle smashed on a pallet of wine the entire thing could explode. Not to mention, nobody wants a black eye from a wayward crown cap that’s been under too much pressure.
This really does what it says on the tin and is perhaps the antithesis to the complexity and handwork required of the traditional method. Any wine can be force carbonated with modern technology; the liquid is simply put in a large, pressurised tank and voila, bubbles. It is cheap to do, and thus generally lower-end sparkling wines are made via this method.
However, as Abe Schoener pointed out when he experimented with this method for his celebrated wine, Blowout,
“perhaps nobody has considered the first wine? If the first wine is of high quality, perhaps the sparkling wine resulting from carbonation can be, too?”
Tank / Transfer Method
For the tank method, a white wine is made, then moved into - yep, you guessed it, a tank - which keeps the CO2 under pressure, essentially copying the role of the bottle in the traditional fermentation but on a gigantic scale. The tirage liqueur is added directly to the tank to commence the second fermentation. After this, the wine may be transferred to another tank (transfer) or it may remain in the original tank. Regardless, dosage will eventually be added if so desired and the wine will be bottled under pressure. Wines made in this way tend to be made with simpler, fruit-forward ways and tend to sit at a cheaper price point.
Col Fondo is the name reserved for the original way to make Prosecco, before the tank and transfer methods were invented. It must, however, be made with grape must (essentially grape juice and solids) to restart the fermentation, as no cane sugar is allowed. This grape must can be stored in a variety of ways - kept in a pressurized and temperature-controlled tank or even frozen.
Natural farming pioneer Angiolino Maule of La Biancara, in the Veneto, creates his Garg’n’Go using this method. His grape must is obtained by drying some Garganega to achieve highly concentrated natural grape sugars. He adds 5% of this juice to 95% of still wine which restarts fermentation. The wine is then bottled with some sugar remaining, to finish fermenting in the bottle.
There are variants on many of these methods; think everything from adding juice to barrels to creating entirely natural secondary fermentations, a la Christoph Hoch, to letting CO2 escape before sealing tanks to creating the highly gluggable, gateway wines of Moscato d’Asti...
...As with everything in wine, there are exceptions to the rules, and variations in almost every technique, but therein lies the fun.