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Regionally distinct wine characteristics (terroir) are an important aspect of wine production and consumer appreciation. Microbial activity is an integral part of wine production, and grape and wine microbiota present regionally defined patterns associated with vineyard and climatic conditions, but the degree to which these microbial patterns associate with the chemical composition of wine is unclear. Through a longitudinal survey of over 200 commercial wine fermentations, we demonstrate that both grape microbiota and wine metabolite profiles distinguish viticultural area designations and individual vineyards within Napa and Sonoma Counties, California. Associations among wine microbiota and fermentation characteristics suggest new links between microbiota, fermentation performance, and wine properties. The bacterial and fungal consortia of wine fermentations, composed from vineyard and winery sources, correlate with the chemical composition of the finished wines and predict metabolite abundances in finished wines using machine learning models. The use of postharvest microbiota as an early predictor of wine chemical composition is unprecedented and potentially poses a new paradigm for quality control of agricultural products. These findings add further evidence that microbial activity is associated with wine terroir.

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Abstract:Wine is an ancient beverage and has been prized throughout time for its unique and pleasing flavor. Wine flavor arises from a mixture of hundreds of chemical components interacting with our sense organs, producing a neural response that is processed in the brain and resulting in a psychophysical percept that we readily describe as "wine." The chemical components of wine are derived from multiple sources; during fermentation grape flavor components are extracted into the wine and new compounds are formed by numerous chemical and biochemical processes. In this review we discuss the various classes of chemical compounds in grapes and wines and the chemical and biochemical processes that influence their formation and concentrations. The overall aim is to highlight the current state of knowledge in the area of grape and wine aroma chemistry.

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