Waiter: "Keep your voice down, sir, or everyone will want them -- according to researchers in France, those protein and sugary leftovers help keep your bubbly bubbly."
Victorious racing drivers are unlikely to care, but the bubbly mousse on the liquid surface is very important to more discerning champagne drinkers. The abundant foam disappears quickly after the champagne is poured, but is then replaced by a 'collar' formed from the bubbles constantly forming and rising through the drink.
A film of bits on the champagne surface, left over from the wine-making process, helps these bubble collars to hang around longer, Michel Valade of the Comité Interprofessionnel du Vin de Champagne in Epernay, France, and his colleagues now report
The finding could help champagne houses make each bottle of wine as bubbly as connoisseurs demand. "The bubble collar is often a lucky consequence of the champagne-making process," says Roger Douillard, one of the research team. "Our goal is to control the process to get nice reproducible results." This could be done, for example, by tweaking the fermentation conditions to leave just the right amount of bits.
"If this can improve consistency, then it has to be good news," says Justin Apthorp, champagne buyer for the UK retailer Majestic Wines. "If you drink a certain bottle in Japan, say, you want it to be the same as if you were drinking it at home."
"Still, I don't know how much demand for this there would be from consumers," he continues. "Sometimes it's quite hard to spot the difference, especially because how clean the glass is makes a big difference to how long the bubble collar lasts." (Cleaner glasses are better.)
The French team had no such concerns: they used crystal glasses repeatedly cleaned in a dishwasher fed with pure, deionized water. After pouring out specially prepared champagnes, one of which had been filtered clean during the production process, they scored each bubble collar on a scale from zero to six, where zero was "no bubble at the periphery of the glass" and six was "wine is covered by a three-dimensional foam".
To judge the amount of leftovers in each wine, they also scanned the champagne surface for a 'macromolecule' film and measured the liquid's surface tension.
Their conclusion: wines with higher residue levels also had thicker, longer-lasting bubble collars. "We suspected this would be the case but this is the first time it has been investigated in champagne," Douillard says. The foam appearance is very important, he stresses, "because the first contact between the wine and you or me as a taster is visual".