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Food and Drink

The science of champagne bubbles

As midnight approaches on December 31, champagne corks will be popping around the world to usher in the new year. But how do you define a particular kind of fizz? The new science of "blaseology" hopes to find out.

The aim was to find a way of slowing down the formation of bubbles in sparkling wine so it would stay fresh for longer. A group of physicists and chemists came together in France, the home of champagne, to work on the problem. They've named their new branch of science "blaseology" - the science of bubbles.

The blaseologists were able to base their research on the centuries-old practices of the champagne-makers. Some 300 years ago they developed the practical methods that cause bubbles to form in the wine. This in itself is a very delicate task.

"When the wine is not yet properly fermented, it's very foamy - it's still incredibly sweet, and it doesn't taste all that good," explains Matthias Driess, a chemistry professor at the Technical University Berlin who has been examining the blaseologists' findings. "If you just bottle this unfermented wine and then open the bottles a few weeks later, it'll be a lot fizzier and not as sweet."

However, the unfermented wine would not be a proper sparkling wine because there are elements that interfere with the flavor.

A man turning the bottles in the Cellars of Codorniu champagne company in San Sadurni d´ Noia (Photo by Pepe Franco/Cover/Getty Images)

The bottles of sparkling wine are put through a sophisticated storage and fermentation process

In order to improve the taste of the wines as they ferment in the bottles, the champagne vintners developed their own techniques. First they used yeast to instigate the fermentation process, during which yeast molecules break sugar molecules down into alcohol and carbon dioxide gas. Most of this gas escapes into the atmosphere.

Shortly before the end of the process, the vintners transfer the wine into tightly sealed bottles, where the carbon dioxide creates pressure five-and-a-half times that of the atmosphere and about twice as high as the pressure in a car tire. This forces the gas to dissolve in the water. The champagne bottles are then put through a sophisticated storage process, which is key to the development of its delicious taste.

Carbon dioxide or carbonic acid?

Glass of sparkling wine.

Champagne bubbles are smaller than those in mineral water

Although it's carbon dioxide that dissolves in both wine and mineral water under pressure, the label on the bottle actually says "contains carbonic acid." The reason for this is the chemical process that causes carbon dioxide molecules to combine with water molecules under high pressure to produce carbonic acid. However, because carbonic acid is a very unstable molecule, it quickly disintegrates again when the bottle is opened and the pressure drops, and then bubbles up as carbon dioxide.

Do the bubbles cool the champagne?

When you unscrew the cap or fire the cork off at the ceiling, you get a reaction like the one in a refrigerator: Gas suddenly expands and, in doing so, cools down. When gas escapes from a canister over a period of time, it can cool the canister down to such a degree that ice crystals may form on the surface. This cooling effect is what you observe, very briefly, just after the cork is popped.

As Driess points out, when you open a bottle of sparkling wine, for a second or two you see a little cloud appear at the neck. "The carbon dioxide that shoots out at the top cools the atmosphere so that the water in the air condenses and forms tiny droplets," he says. However, the cooling effect is very brief. "If you haven't put the champagne on ice beforehand, that alone won't cool your wine."

Big bubbles, little bubbles

If you compare glasses of freshly-poured mineral water and sparkling wine, you'll immediately notice one big difference. The bubbles in sparkling wine are much smaller, and they usually originate from a particular part of the glass. In mineral water, on the other hand, the bubbles are practically jostling for position.

"There's a reason why it's called 'mineral water,'" explains Driess. "There are minerals dissolved in the water, and they cause the water to be hard or soft."

If the water contains a lot of minerals, gas is expelled from the liquid more forcefully and haphazardly.

Wine glasses full of wine one on another forming a pyramid.

Better to drink the whole bottle - you don't want it to go flat

But there's also another reason why the bubbles in sparkling wine rise to the surface so neatly, as if on little filaments. The bubbles keep forming at the same spot.

The blaseologists used microscopic photography to document the formation of the bubbles, and discovered that these points of origin fell into two categories. Either they are particles of dust floating in the wine, possibly left on the glass by a cloth, or they're tiny scratches in the surface of the glass itself. They are the catalysts that cause the carbonic acid to degenerate into carbon dioxide.

Biochemistry on the tongue

But the carbon dioxide isn't just there to please the eye: It also makes a difference to the taste. Surprisingly, the fizzy, refreshing effect doesn't come from the beads of carbon dioxide that form in the glass - it comes from actual contact with the carbonic acid.

In the mouth the sparkling wine penetrates to the lower layers of the rough surface of the tongue. There it comes into contact with an enzyme in the body that further enhances carbon dioxide formation. It's this enhanced reaction that causes our nerves to respond and register the tingling feeling we associate with sparkling wine. To prove the point, people taking medication that inhibits the production of this enzyme report that even the best champagne tastes flat and stale.

The myth of the silver spoon

So if you've only managed to drink half of your bottle of champagne, how do you make sure it'll still taste good the following day? In Germany the conventional wisdom is that you should stick a silver spoon into the neck of the bottle. But Driess says he can't see any reason why that would work. "Experiments have proven that this makes no difference at all. What's more important is to make sure the champagne is kept cold."

Warmth supplies energy for the chemical reaction that turns carbonic acid back into carbon dioxide.

Driess does have a surprising tip, though. "You shouldn't put the cork back in the bottle when you put it in the fridge. It might feel all wrong at first, but try it: It's really true!"

As a connoisseur of sparkling wines, he of course knows how champagne should really be enjoyed. "The best way," he says, "is just to drink the whole bottle."

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