Bubbles that add sparkle to wine
Bubbles add sparkle to wine. How they form, move, and affect our perception of the wine is the subject of the science of champagne. I stumbled on this topic in a review on the chemistry and physics of champagne published in the Journal of Agricultural and Food Chemistry. The review comes from the keyboard of Gérard Liger-Belair, a physicist who is a professor at the Université de Reims, in Champagne-Ardenne, France (where else?). While still a student, he used high-speed photography (strong fast flashes and very sensitive cameras) to photograph the bubbles of carbon dioxide (CO2) in champagne and has been pursuing the subject since. Liger-Belair has even published a book on the science of champagne , which I have yet to read, but his review articles have been the source of some great tidbits:
The cork pops at 40 mph
The pressure inside the bottle is about five times normal air pressure. Just letting that cork pop will eject it at 50 to 60 kilometers per hour.
Your glass has 2 million bubbles
If your holding a typical flute glass, most of the CO2 escapes not as bubbles, but molecule by molecule through the champagne surface. Only 20% of the CO2 ends up as bubbles. Champagne in a flute glass has a smaller surface in contact with the air, which helps slow down the loss of CO2. In a regular wine glass the bubbles would not last as long.
You need bubbles to make bubbles
You need bubbles to give birth to bubbles. Older work on bubble formation speculated that the bubbles in sparkling drinks form around the irregularities of the glass. Liger-Belair and collaborators have photographed air bubble trapped in cellulose matter (basically bits of towel or paper) that is stuck to the glass surface. These bubbles are miniature air-champagne surfaces that expand as the dissolved CO2 in the wine diffuses in. Eventually the trapped bubble breaks into two and the process repeats.
Without the trapped bubbles there will be no bubbles. Liger-Belair poured champagne into a super clean glass and it did not bubble. In one of his talks he showed a flute with a laser-etched trap for air bubbles. The trap is shaped in a ring and produces a beautiful bubble flow.
Champagne sprays you with its aromas
The bubbles of champagne float on the surface like miniature icebergs. And then they pop spraying little droplets with whatever molecules happen to be on the surface. These droplets float through the air carrying the molecules that give wines their rich flavor. There is no need to swirl your champagne to enjoy its aroma.
A few links to explore the science of champagne:
- Advances in the science of champagne bubbles (Royal Society of Chemistry)
- Bubbles and flow patterns in champagne (American Scientist)
- Podcast by Liger-Belair (New York Academy of Sciences)