Can Microbes Help Scientists Crack Wine’s Terroir Code?

Scientists in New Zealand and the U.K. may be one step closer to understanding the mystery of how terroir shapes a wine. They’ve found that microbes, specifically those tiny winemakers called yeast, play a larger role in a wine’s regional identity than previously understood.

Researchers from the University of Auckland and the University of Lincoln in the U.K. isolated strains of Saccharomyces cerevisiae, the primary species of yeast used to turn grape juice into wine, from six New Zealand regions and discovered that different regional strains produce distinct aromas and flavors.

“Classically the concept of terroir was thought to be driven by some complex mix of the particular climate and soils vines grow in, overlaid by the way the vines are managed,” said Dr. Matthew Goddard, a biological sciences professor at the University of Lincoln and coauthor of the report. “No one really considered the role of microbes.” That changed when research found regional differences in various yeast strains.

For the study, published in Nature’s Scientific Reports, the team isolated yeast populations from six different growing regions in New Zealand, using samples from wineries in Nelson, Martinborough, Hawkes Bay, Central Otago and the Awatere and Wairau Valleys (both in Marlborough). They identified which strains of Saccharomyces cerevisiae were distinct to each area.

To test the yeast’s effect on wine, they sterilized Marlborough Sauvignon Blanc juice, removing any other yeast strains hitching a ride, and fermented it in six lots, using a different strain with each batch. The wines were then analyzed for concentrations of 39 different chemical compounds responsible for producing various flavors and aromas that are derived from the fermentation process.

The tests found that levels of 29 of the compounds varied according to the regional yeast strain. Yeast from Nelson on New Zealand’s South Island had greater concentrations of the chemicals perceived as apples and sweet fruits than Central Otago and Martinborough. The Awatere and Wairau strains, on the other hand, had more of the compounds that create floral, apple and honey aromas and flavors.

The results surprised Goddard, who didn’t expect to find any variations. “I think the classic ideas of climate and soil are the main drivers of terroir, but this shows that microbes have a small but significant effect,” he said, noting that no study has quantified how much of an effect it is.

For winemakers, the findings add one more factor in deciding which yeast should be fermenting their wines. Various cultured strains are already known to produce distinct flavors and styles. Some winemakers argue that ambient yeasts, rather than strains winemakers have selected, produce more distinctive local flavors despite their unpredictability, and the study seems to supports this theory. Others prefer to rely on commercially cultivated strains, which are more efficient and less likely to break down during fermentation.

Can Microbes Help Scientists Crack Wine's Terroir Code

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