Wednesday, 7 March 2012

I want this job: 5 secrets found behind champagne

Opening the champagne to celebrate occasions like a wedding, a graduation, a job promotion or the weekend is always awesome.  You hear that 'POP' and then the party suddenly magically begins.  What do we really know about champagne.  It took some researchers, a high speed camera and many many bottles of champagne to find out.  (I wonder what the grant proposal would have looked like for this research.)

Gerard Liger Belair studies the bubbles in Champagne

1) the surface tension in champagne bubbles use champagne bubble with a radius of  R ~ 0.1 mm, and a pressure of P ~ 1000 Pa ~ 10-2 atm ~ 50 mN/m.  In comparison a soap bubble is soap bubble: R ~ 5 cm, surface tension~ 35 mN/m, P ~ 3 Pa ~ 3.10-5 atm.  Laplace Law calculates these for a bubble. 
See a presentation by the group that studied the champagne.

2) yeast eats sugar and excretes alcohol and carbon dioxide (CO2).  This fermentation process was developed by the Benedictine monk from the 17th century Dom Pierre Perignon (all the good things religion has brought).  Before sealing the champagne bottle the CO2 is dissolved in the wine.  Champagne wines are supersaturated with the dissolved gas molecules, which form together with the ethanol during the second fermentation process, or the 'prise de mousse'. The bottles are sealed and stored in cool cellars to allow the CO2 molecules to gradually dissolve.

3) How does one person study champagne bubbles?  They use a high speed camera to take snap shots of at each stage in the bubbles short life to explain the forces they play.  Scientist Gérard Liger-Belair of the University of Reims did this for the journey of a trillion microscopic bubbles.

4) What did they find?  In a 75 cl bottle of champagne (costing around 40 euros minimum) it contains about 9 grams of dissolved CO2.  Each bubble has an average size of 0.5 mm.  The number of bubbles released in one bottle is about 1 million.  Nucleation from impurities inside the champagne glass (dirt, soap residue, cracks for example) birth this process.  The bubbles then rise to the top of the glass at the water interface and burst on the surface. 

5) What can we do with this?  Besides getting the researchers drunk we can fine tune the champagne production and calculate the amount of fermentation of sugar needed to produce enough bubbles for the champagne.  The amount of dissolved CO2 is important 'as it affects the bubble count in the glass, the growth rate of rising bubbles, the mouth feel of collapsing bubbles and aromatic sense it creates, or its so-called bouquet.'   The three grape varieties used Chardonnay, Pinot Munier and Pinot Noir all play a part in how good the champagne is and is up to the growers and blenders to see how this mix, the growing patterns around the Champagne region of France get impart its taste.