The science of bubbles
BY JENI PORT
The bubble. It rises, it breaks, it collapses. Totally spent.
It’s a short, frenetic life, a disciplined one too, doing the job it was created for and then calling it a day.
And that job? Tickling, prickling and popping pretty much sums it up, but if you’re a bubble hard at work in a sparkling wine or champagne, there’s more to it.
A lot more.
The bubbles in a glass of champagne or sparkling wine – all 11 million plus of them – are produced by yeast during a second fermentation in the bottle, what’s often called method champenoise, after the traditional approach in Champagne.
“It’s really, really beautiful science,” says Dr Kate Howell, a lecturer in food chemistry at the University’s Faculty of Veterinary and Agricultural Sciences.
Howell and her students are attracted to all the things we don’t know about bubbles in sparkling wine. Turns out it’s plenty.
As the daughter of Canberra winemakers and a microbiologist who has worked in wine, her interest is possibly more piqued than most. Her University colleague, Dr Sigfredo Fuentes is a plant physiologist and a senior lecturer in wine science.
“The original idea was from Sig,” says Howell, “who has used image analysis to do lots of work in vineyards, and he started talking about an idea with sparkling wine.”
And so, the first part of their research was to see if there was a way to predict quality sparkling wine simply by looking at wine in the glass.
They chose 30, medal-winning Australian sparkling wines judged at the 2013 Melbourne Wine Show, built an automatic pourer – something that would pour the same quantity (40mls), at the same rate, time and time again – and attached it to a box with lights on the inside.
Then image analysis, infrared spectroscopy and a statistical computer program were brought in to take photos and analyse each wine in the glass after pouring, concentrating on the bubbly foam as it rose and fell.
Carbon dioxide molecules escape through bubbles when they latch on to impurities on a wine glass wall (such as fibres from paper or cloth used to clean glasses) and rise through the wine to the surface and explode, delivering to the nose all kinds of yeasty, fruity smells.
The greater the number of starting points for the bubbles in a glass, the greater the number of bubbles and the denser the foam that gathers around the edge of the glass.
Was it possible to predict a quality sparkling wine on the foam and the time it lasted in the glass? Yes, it was.
Not all sparkling wines recorded the same time for the rise and collapse of their bubbly foam. Some bubbles lasted 250 seconds but one – the gold medal winning 2009 Blue Pyrenees Estate Midnight Cuvee blanc de blancs – lasted more than an hour.
Researchers found the longer the foam lasted in the glass directly related to the ranking given to the wine.
“We now know that things like protein can affect the size of the bubble and how long the foam will persist,” explains Howell (GCertUniTeach 2012). “But it’s still a relatively unknown field of wine science.”
With the first part of their research completed, Howell and Fuentes are moving into the next phase.
Students are working with Blue Pyrenees Estate, in Victoria’s Pyrenees region, and Domaine Chandon, in the Yarra Valley, to see if they can find a correlation between protein, bubbles and the fermentation/ageing process of sparkling wines.
In the meantime, Dr Howell is in Montpellier in the south of France for a year working with a French research group studying wine yeast.
Part of her work will take her to the home of the bubble, Champagne, and into the inner research sanctums of some of that region’s greatest champagne makers.
This bubbly story is far from spent.