Abstract
Aims: Determinants of the terroir effect in Riesling were sought by choosing vine water status as a major factor. It was hypothesized that consistent water status zones could be identified within vineyards, and, differences in wine sensory attributes could be related to vine water status.Methods and results: To test our hypothesis, 10 Riesling vineyards representative of each Ontario Vintners Quality Alliance sub-appellation were selected. Vineyards were delineated using global positioning systems and 75 to 80 sentinel vines were geo-referenced within a sampling grid for data collection. During 2005 to 2007, vine water status measurements [leaf water potential (ψ)] were collected bi-weekly from a subset of these sentinel vines. Vines were categorized into “low” and “high” leaf ψ zones within each vineyard through use of geospatial maps and replicate wines were made from each zone. Wines from similar leaf ψ zones had comparable sensory properties ascertained through sorting tasks and multidimensional scaling (2005, 2006). Descriptive analysis further indicated that water status affected wine sensory profiles, and attributes differed for wines from discrete leaf ψ zones. Multivariate analyses associated specific sensory attributes with wines of different leaf ψ zones. Several attributes differed between leaf ψ zones within multiple vineyard sites despite different growing seasons. Wines produced from vines with leaf ψ >-1.0 MPa had highest vegetal aromas whereas those with leaf ψ <-1.3 MPa were highest in honey, petrol and tropical fruit flavors. Vines under mild water deficit had highest honey, mineral, and petrol and lowest vegetal aromas.Conclusion: Results indicate that water status has a profound impact on sensory characteristics of Riesling wines and that there may be a quality threshold for optimum water status.Significance and impact of the study: These data suggest that vine water status has a substantial impact on the sensory properties of Riesling wines. Variability of leaf ψ within vineyards can lead to wines that differ in their sensory profiles. These findings were consistent among vineyards across the Niagara Peninsula. These strong relationships between leaf ψ and sensory attributes of Riesling suggest that vine water status is a major basis for the terroir effect.
Highlights
Terroir-related studies have been performed with focus on single variables such as soil (Seguin, 1975) and climate (Tonietto and Carbonneau, 2004)
Consistent leaf ψ zones were found within vineyard blocks and these zones produced wines with different sensory profiles of which several attributes were similar across multiple vineyards across the Niagara Peninsula, Ontario
These differences existed without any vineyard manipulation or cultural practice imposed onto the vines meaning that vine water status is a major factor of the terroir effect
Summary
Terroir-related studies have been performed with focus on single variables such as soil (Seguin, 1975) and climate (Tonietto and Carbonneau, 2004). While several have looked at characteristics of soils, including chemical constituents, many have indicated that the soil’s physical properties involved in regulation of water supply to the vine are the most critical with respect to the terroir effect. Vine water supply has been noted as a major factor in the terroir effect due to its impact on early budburst potential and potential vine vigor (Morlat et al, 2001). Grapes cultivated under mild water stress can improve berry composition (Matthews and Anderson, 1988; Smart, 1985) and mild water deficits have been shown to be a major factor in the terroir effect (Seguin, 1983; van Leeuwen et al, 2004; 2009)
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