Progress in sparkling wines: bubbles and flow

A progress report from Gérard Liger-Belair, the world authority on wine bubbles, and his quest to define the ideal glass for enjoying the effervescence of champagne. Bubbling really stirs up a glass of wine, and if you're going to etch a glass to generate bubbles, you'll need to adjust the pattern to the glass shape.

When a sparkling wine is poured into a glass, the bubbling delivers aroma and pleasantly irritating carbon dioxide to our nose. At the same time it depletes aroma, gas, and its own activity. If a glass of sparkling wine bubbles vigorously, it loses the advantages of effervescence quickly; if it bubbles too slowly, it has no charm. Liger-Belair has shown that steady, regular, "pleasing" bubbling is caused by plant dust: microscopic cellulose fibers from the dish towel or released into the air from such things as clothes and paper. Intentionally scratching or etching the bottom of the glass creates pits that induce more predictable bubble formation, but the bubbling is faster, coarser, and more chaotic.

For this new study, Liger-Belair and colleagues added tiny reflective plastic beads to bottles of champagne, poured the wine into glasses with bubble-forming pits etched just above the central stem, illuminated the glasses from the side with a laser beam, and used time-lapse photography to follow the movements of the beads.

They found that bubbles rising from the bottom of the glass pull the surrounding liquid along with them, setting up regular lines of flow from the bottom of the glass to the top and then back down. In a tall flute, the lines of flow run through the full volume of the liquid, and deliver bubbles directly to the edge of the glass to form the desirable collerette or bubble collar. But in a broad and shallow coupe, the flow lines ran only in the center of the glass, leaving a surrounding "dead zone" of little or no effervescence that prevented the delivery of bubbles to the edge.

So glasses with different shapes will have to be etched with different patterns of pits to deliver the same desirable effervescent effects. The large surface area of wine exposed in a coupe also means a more rapid loss of gas, so the etching in a coupe may need to be sparser than in a narrow flute.

Next on the agenda for the Liger-Belair lab: "quantitative measurements of the release of volatile organic compounds and carbon dioxide from glasses showing various engravement and shape conditions, our final goal being to scientifically identify the best glass for the tasting of champagne and sparkling wines in terms of gas discharge and flavor release."

In the meantime, fans of sparkling wine have more to look for in the glass.

__________________________________

Liger-Belair, G. et al. Visualization of mixing flow phenomena in champagne glasses under various glass-shape and engravement conditions. J. Agric. Food Chem. 2007, vol. 55.

Published on the web: http://dx.doi.org/10.1021/jf062973+