Terroir is the term for the unique blend of a vineyard’s soils, water and climate that impacts the flavor and quality of wine. These unique microbial inputs are key to regional wine fermentations.
A new study from UC Davis, MicroTrek, Inc. and Constellation Brands Inc. offers evidence that grapes and the wines they produce are also the product of an unseen but fairly predictable microbial terroir, itself shaped by the climate and geography of the region, vineyard and even individual vine.
Results from DNA sequencing revealed that there are patterns in the fungal and bacterial communities that inhabit the surface of wine grapes, and these patterns are influenced by vineyard environmental conditions.
To examine the microbial terroir, the researchers collected 273 samples of grape “must,” –- the pulpy mixture of juice, skins and seeds from freshly crushed, de-stemmed wine grapes. The must samples were collected right after crushing and mixing from wineries throughout California’s wine-grape growing regions during two separate vintages. Each sample, containing grapes from a specific vineyard block, was immediately frozen for analysis.
The researchers used a DNA sequencing technique called short-amplicon sequencing to characterize the fungal and bacterial communities growing on the surface of the grapes and subsequently appearing in the grape must samples.
They found that the structure of the microbial communities varied widely across different grape growing regions. The data also indicated that there were significant regional patterns of both fungal and bacterial communities represented in Chardonnay must samples. However, the Cabernet Sauvignon samples exhibited strong regional patterns for fungal communities but only weak patterns for bacterial communities.
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Read the article published on PNAS 2013 :
Nicholas A. Bokulich, John H. Thorngate, Paul M. Richardson, and David A. Mills, ‘Microbial biogeography of wine grapes is conditioned by cultivar, vintage, and climate ‘, doi:10.1073/pnas.1317377110
