Hearing, sight, smell, taste and touch.
The effervescence in Champagne is a large part of the fascination of bubbly even though we still don’t really understand the complex phenomena behind it.
Sparkling wine has a unique ability to stimulate all of the senses: hearing, sight, smell, taste and even touch — how the wine feels in your mouth and on the tongue.
The stimuli received by the ear, the eyes, the nose and the mouth combine to produce an intense pleasure that makes Champagne the natural choice for festive occasions. The experience is more vivid and immediate than with still wine.
Champagne produces an unmistakable sound that rises when the bottle is opened, falls as the wine is poured then drops to a whisper as the bubbles collect to form the mousse.
In a recent study, Patrice Simard of the University of Compiègne measured the sound released from a glass of Champagne. The experiment was conducted in a specially-built room inside a building with a foundation on sand. The floor and walls of the room were lined with a one-meter thick layer of mineral wool to prevent any kind of sound reflection. The result was an anechoic (soundless) chamber: a place so eerily quiet that the person inside it could hear their own heartbeat, and the blood gently pumping through their head.
Modern equipment was used to capture the sound made by Champagne: first the popping noise as the bottle is opened; then the sound of the wine being poured; then the discreet sound of the mousse. Calculations were then performed on those sounds in digital form, producing a sound image that showed how the evolution of the acoustic signal varied widely with each successive stage.
While the sound made by still wine is extremely transient, the sounds made by Champagne continue to evolve over several tens of seconds. Another key difference is that the type of glass (crystal or otherwise) has a direct effect on bubble behaviour — how the bubbles form, how they collect in a ring at the surface and in particular how they are constantly replaced by new bubbles. The sound produced by the same Champagne was found to be quite different depending on the type of glass used.
The phenomena behind the effervescence and the mousse in Champagne are described in the "Effervescence" booklet published by the CIVC as part of the series entitled "The Keys to the Wines of Champagne".
Roger Douillard and Bertrand Robillard have shown that the bubbles in a glass of Champagne are released from so-called nucleation sites. These are micro-cavities on the sides or bottom of the glass together with particles suspended on the surface of the wine itself (usually specks of dust or traces of fibre deposited by a tea-towel).
Using a glass that had been specially cleaned and treated, Robillard showed that without nucleation sites, there is no effervescence and so no mousse either. Productive nucleation sites, on the other hand, generate an endless stream of bubbles,which rise at a rate of 10-20 bubbles per second from each site. So depending on the number of nucleation sites, there can be anything from a few strings of tiny bubbles to dozens in a single glass of Champagne. The driving force behind bubble ascent is buoyancy (also known as the Archimedes Principle. As the bubbles rise to the surface they draw in the dissolved carbon dioxide in the wine, which causes the bubbles to swell and collect at the top of the glass in a snowy layer called the mousse
Once a bubble reaches the surface of the wine, one of two things can happen. Either it shrinks or it bursts if the film of wine that separates the bubble from the air is disturbed. As a bubble bursts, tiny droplets of Champagne are ejected into the air by as much as several centimeters. But unlike say, lemonade, that rapidly loses its fizz, Champagne has the advantage of amphiphilic macromolecules, so called because they combine wine-friendly elements with wine-repellent elements that thrive in the presence of carbon dioxide. Amphiphilic macromolecules exist at the wine/air interface and serve to stabilize the mousse by slowing down the rate of bubble shrinkage and preventing the bubbles from bursting.
As demonstrated by Roger Douillard using ultrafiltration of these macromolecules, the richer their presence in a wine the more stable the mousse and vice versa. When they reach the surface, the bubbles collect against the sides of the glass to form the ring, the so-called collerette at the top of the flute. But this is the not stable process it appears to be. In tests conducted by Robillard, lipstick was shown to have a devastating effect on the mousse in Champagne and so too was dishwasher rinse-aid. The wine you see in the glass actually conceals a world of complexity of which most of us are unaware. There is something mesmerizing about watching the bubbles in a Champagne flute, like gazing at the dancing flames in a fireplace.
Carbon dioxide certainly adds a certain something to the smell and taste of Champagne but what that is exactly has yet to be fully explained by sensory analysis. One thing we do know for sure is that the mouth plays a significant role in our conscious perception. Carbonated drinks act as powerful stimulants for the central nervous system, exerting a mechanical-chemical effect that starts with an almost instantaneous slight stinging sensation and then morphs into something more prolonged. To put it another way, carbon dioxide causes pain.
Hence the need for well-behaved bubbles, enough to produce a tingling not a burning sensation. Champagne wines are distinguished by a soft, almost caressing effervescence that chimes perfectly with the other sensations aroused by the wine.