Abstract
ABSTRACTRegionally 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.
Highlights
Regional variations in wine quality traits, collectively referred to as “terroir,” have been documented empirically for centuries, but few conclusive links have been drawn between regional factors and wine sensory properties
We demonstrate that the grape/wine microbiota and metabolites are regionally distinct, the must and wine microbiota correlate with the wine metabolome and fermentation performance, and grape must microbial composition predicts the metabolite composition of the finished wine, suggesting that microbial dispersion patterns may contribute to regional wine characteristics
Red and white wine fermentations were sampled at different time points, as they are processed differently: white grapes are crushed and pressed immediately, and the clarified juices are fermented, whereas red grapes are crushed and fermented as must, which is only pressed after fermentation is complete (Table 1)
Summary
Regional variations in wine quality traits, collectively referred to as “terroir,” have been documented empirically for centuries, but few conclusive links have been drawn between regional factors and wine sensory properties. Geographical pedigree is legally protected, e.g., through the Protected Designation of Origin regulations in Europe and American Viticultural Areas (AVAs) in the United States Such regionality can be distinguished by chemical composition [1,2,3] and sensory characteristics [4,5,6,7], but establishing which conditions drive quality outcomes remains tenuous. In addition to directly influencing wine chemical composition, understudied microbes could indirectly alter wine quality— e.g., by inhibiting fermentation progress or malolactic fermentations To address these issues, we conducted an exploratory study to assess (i) whether the grape microbiota and wine metabolomes exhibit distinct patterns of distribution at small geographic scales (e.g., neighboring vineyards), (ii) whether regional wine microbiomes and metabolomes are correlated, and (iii) associations between the microbiome, fermentation performance, and prefermentation grape must/juice characteristics. We demonstrate that the grape/wine microbiota and metabolites are regionally distinct, the must and wine microbiota correlate with the wine metabolome and fermentation performance, and grape must microbial composition predicts the metabolite composition of the finished wine, suggesting that microbial dispersion patterns may contribute to regional wine characteristics
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