(CosmosMagazine) - In vino veritas – in wine there is truth – says the Latin proverb, but the truth behind how grapes ferment into a unique vintage is a mystery long cloaked by the term terroir. Andrew Masterson finds that science is finally peeling back the curtain.

Coldstream in mid-winter is living up to its name. The township lies deep within the Yarra Valley, a region on Melbourne’s northeast fringes celebrated for its cool-climate wines. The hillsides are lined with vines – brown, gnarled and leafless but shimmering, this morning, in a thick cloak of frost.

The vines may lie dormant, but inside the cellars of Oakridge winery the annual ferment is seething with microbial life. A couple of batches are moving a bit slowly, says chief winemaker and Oakridge chief executive David Bicknell, but that’s par for the course. When the production of fine wine relies wholly on the vagaries of the indigenous microbial population, the process never runs like clockwork.

“With commercial yeast you get certainty – you can sleep at night,” says Bicknell. “But how do you make wine more interesting? You exploit the metabolic processes of different yeast species.”

Bicknell’s faith in wild yeasts adds stress at fermentation time, but the pay-off is multi-award-winning wines regularly acknowledged as some of the best in Australia. “The wines do taste different, even if there’s no way you can show that statistically,” Bicknell says. “The only way to really know is to taste.”

Exploiting the diverse and fluctuating populations of wild yeasts found on the plants, fruit and in the air of vineyards is “the new black” (not to mention red and white) in oenology. The practice is becoming more commonplace among artisan winemakers. Even some of the giant commercial wine corporations are investing in the method.

Wild fermentation, says Bicknell, represents the intersection of science, craft and philosophy. But it could also form the basis of a profound shift in the narrative of wine. The more we study winemaking’s microbes, the more it appears they might explain one of the wine industry’s most beloved, but vaguest, terms: terroir.

“Terroir is a wonderful marketing term,” says David Mills, a microbiologist at UC Davis, who studies microbes in wine. “But it’s not a science.”

The French word terroir is difficult to translate. The closest translation is “soil”, but that is just one of its components. Terroir connotes the unique sense of place – the soils, the topography and the microclimate. It’s what makes the wines of Bordeaux or Australia’s Coonawarra so distinctive, and so inimitable.

Sommeliers like Ren Lim, former captain of the Oxford University Blind Tasting Society (and a PhD biophysics student) will tell you merely from swirling a mouthful of Cabernet Sauvignon which Australian winery produced it.

“The ones from Margaret River often give off a more pronounced green pepper note, a note found commonly in Cabernets grown in regions which experience pronounced maritime influences. Coonawarra Cabernets are somewhat different and unique in their own way. They are often minty and have a eucalyptus or menthol note in addition to the usual ripe blackcurrant notes. The green pepper note is often suppressed under the menthol notes. Nonetheless, the Cabernet structure remains in both these wines.”

It’s a feat that Mills does not question. “I don’t doubt regionality exists, but what causes it is a whole other set of issues.”

Terroir has so far eluded science. But that may be about to change. And many places will be avidly watching this science. As climate change plays havoc with existing wine growing regions, new contenders to the wine industry – such as China – will stand to gain from demystifying the secrets of fine wine.