Scientists have found that wild yeasts vary from region to region, and can have a unique influence if used in the wine-making process.
Climate, soil and geography have long been recognised playing an important role in shaping the character of a region's wines and whose interplay is at the heart of the French concept of terroir. However, a breakthrough by New Zealand scientists now suggests that an area's yeasts could play their part in regional differences as well, with the discovery that communities and strains of wine yeasts vary from region to region.
As well as playing their crucial role in a wine's alcoholic fermentation, yeasts were already known to be responsible for a significant portion of the compounds that can be smelled and tasted in a wine. But proving that different regions possessed significantly different yeast populations, is a world first.
Conducted by Velimir Gayevskiy and Dr Matthew Goddard of the School of Biological Sciences at the University of Auckland and funded by NZ Winegrowers and MSI, the study detected distinct differences between the so-called "wild" or "indigenous" yeasts found on syrah and chardonnay grapes and in their corresponding spontaneous ferments in three separate New Zealand regions.
Wild yeasts are those that exist naturally on grapes and in the vineyard, which left to their own devices will spontaneous start a grape's fermentation into wine. However, nowadays many wines - especially those made in larger volumes - will be inoculated with cultured yeasts. These behave in a more predictable and reliable manner than their wild counterparts and can be selected by the winemaker for specific characteristics.
In the light of these findings, winemakers wanting to make wines most expressive of a specific place might want to dispense with generic yeasts from a packet and let nature take control of their ferments, as was the way in the past. An earlier study by Goddard already proved that New Zealand's yeasts more generally were something special, in being a genetically distinct population of the main wine yeast, Saccharomyces cerevisiae.
Surprisingly, research into regionally specific yeast populations is currently confined to New Zealand. Not even France, that bastion of regional difference and respected centre of wine research has probed their yeast populations so deeply.
However, Goddard surmises similar results could be seen across other winemaking nations. "My gut feeling is that New Zealand isn't the only country that can objectively claim this difference," he tells me. "I wouldn't be surprised if this was the same in other parts of the world, but that remains to be seen."
Yeasts do appear to get about a bit though. Earlier Goddard detected what appeared to be French yeasts that had hitched a ride in new barrels imported from France and in this recent study found evidence that some yeasts maybe being moved between regions.
This discovery of regionally specific yeasts opens up a whole new chapter in research into the complexities of these single-cell fungi and their applications in wine. Goddard and his team now plan to look into what's driving these differences, which could be down to natural selection and related to factors such as climate.
Another exciting angle they're about to pursue is attempting to identify the yeasts responsible for specific aromas and flavours that could contribute to a regional signature. These could then potentially go on to be isolated and then harnessed by winemakers to make wine with particular strong regional characters.
"For the first time, these findings suggest that yeasts could be part of that regional influence and of a wine's terroir," Goddard states. "This is important as it not only adds to the story or provenance behind a region's wine, but it may also afford New Zealand winemakers local novel tools to help ensure New Zealand continues to produce high-quality, distinctive wines."
Wines that have benefited from our local yeasts:
Fancrest Estate Di's Waipara Pinot Noir 2009 $32
Biodynamic from its inception and pinot noir-focused, Fancrest is a new Waipara Estate that's one to watch. Its latest release has a gossamer-like texture and unfurls to display layers of pretty cherry plum fruit, florals, savoury spice and hints of smoke and game.
Odyssey Reserve Iliad Gisborne Chardonnay 2010 $36
A wild barrel ferment has likely added to the texture of this rich chardonnay, with its toasty palate of ripe fig, stone fruit and savoury undertones counterpoised by fresh citrus. (From Glengarry, Caro's, Wine Vault, Fine Wine Delivery Company.)
Pasquale Waitaki Valley Pinot Gris 2010 $27
Some winemakers opt to include a portion of wine that's been fermented by wild yeasts for complexity, as is the case of this intense drier style of pinot gris with its notes of crisp apple and nashi pear, infused with ginger, mineral and hints of hazelnut. (From Wine Vault, Caro's, The Merchant of Tirau, Point Wines, Primo Vino.)