Terroir 2016 banner
IVES 9 IVES Conference Series 9 Terroir factors causing sensory and chemical variation in Riesling wines

Terroir factors causing sensory and chemical variation in Riesling wines

Abstract

The term “terroir”, originated in France, comprises the interaction of soil, climate, and topography with the vines of a specific variety and may be extended to the human impact due to the active choice of viticultural and oenological treatments. Although geological diversity has been described for many vineyard sites, there is only scarce scientific knowledge about how the specific soil or climatic conditions translate into specific sensory differences.

To investigate the sensory impact of terroir, a range of 25 highly diverse vineyard sites were selected in Germany. Riesling grapes were harvested from those sites during five consecutive vintages, which were either processed following a standardised winemaking protocol or according to customary winemaking in the respective wine estate. Eight to ten months after harvest, a descriptive analysis by 20 trained judges characterised the wines by one colour, 14 odor and five taste attributes.

According to sensory analysis, wine originating from different vineyard sites yielded a considerable variation, although they were in close proximity. For example, throughout five vintages wines made from Riesling grapes grown on a loamy loess soil with basalt stones were much more intense in its citrus, peach, mango and honey melon attributes than the wines produced from light colored sandstone, which was described as more sour with vegetative and mineral notes. Applying discriminant analysis, it was possible to group the five bedrock types according to their sensory properties, and identify their typical aroma attributes.

Combining sensory and site specific data, PLS analysis was able to explain 48% of the sensory variation by a combined soil/climate data set with first two dimensions. The highest coefficients of determination were obtained for the explanation of sourness-related attributes (R2 0.82 – 0.94), which correlated with precipitation during the ripening period and the gravel content of the soil. The odour of honeydew melon was related to the sum of growing degree days, calcium and clay content of the soil plant available water.
Extracted flavor compounds of the wines were also analysed by GC-MS and used to group different terroirs. Furthermore, concentration of flavor compounds could be linked as well with soil and climate data using PLS-regression as well as to link them with sensory perception. 

Overall, this research could address specifically the impact of individual versus standardized winemaking, since wines were obtained from both sources, but from identical grape material. Throughout five vintages and 24 vineyard sites, customized winemaking was superior to distinguish the different terroirs to a greater extent than standardized winemaking.
Based on the analysis of up to 105 wine samples the impact of terroir could be demonstrated on a very robust data basis. Knowledge gained on how site-specific soil and climate parameters contribute to sensory differences in the wines will be an important contribution to communicating the concept of terroir to consumers.”

DOI:

Publication date: June 24, 2020

Issue: Terroir 2016

Type: Article

Authors

Ulrich Fischer (1), Andrea Bauer (2), Stefan Koschinski (3), Sascha Wolz (1), Anette Schormann (1) and Hans-Georg Schmarr (1)

(1) Institute for Viticulture and Oenology, DLR Rheinpfalz, Breitenweg 71, 67435 Neustadt/Wstr. Germany.
(2) Department of Life Sciences, University of Applied Science, Hamburg, Germany
(3) Almsco/Markes International, Germany

Contact the author

Keywords

Terroir, wine, viticulture, Riesling, aroma compounds

Tags

IVES Conference Series | Terroir 2016

Citation

Related articles…

Impact of changes in pruning practices on vine growth and yield

A gradual decline in vineyards has been observed over the past twenty years worldwide. This might be explained by the climate change, practices change or the increase of dieback diseases. To increase the longevity of vines, we studied the impact of different pruning strategies in four adult and four young vineyards located in France and Spain. In France, vineyards were planted with Cabernet franc on 3309C while Spanish trials were planted with Tempranillo grafted on 110R. Vegetative expression, yield, quality of berries and wood vessels conductivity were measured. The distribution of vegetative expression, yield and berry composition between primary and secondary vegetation were quantified. Finally, tomography was used to evaluate the implication of the treatments on sap flows.
First results show that i) the respectful pruning leads to an increase of 30 to 50% more secondary shoots than the aggressive pruning in France and between 15 and 20% in Spain, ii) there is no major effect on the yield over the first two years following the implementation of the new pruning practices, although the proportion of clusters from suckers is higher on the respectful pruning method. On young vines, the development of the trunk according to a respectful pruning leads to a loss of harvest 2 years after planting. This is due to the removal, on the future trunk, of the green suckers which carrying bunches. This operation carried out in spring rather than during winter pruning, would promote a better leaf / fruit balance when the plant comes into production, and could lead to better hydraulic conduction in the vessels of the trunk. Maintaining these trials for several years will provide more robust data to assess the impact of these practices on the vines over the long term.

Investigating the impact of grape exposure and UV radiations on rotundone in Vitis vinifera L. Tardif grapes under field trial conditions

Rotundone is the main aroma compound responsible for peppery notes in wines whose biosynthesis is negatively affected by heat and drought. Through the alteration of precipitation regime and the increase in temperature during maturation, climate change is expected to affect wine peppery typicality. In this context there is a demand for developing sustainable viticultural strategies to enhance rotundone accumulation or limit its degradation. It was recently proposed that ultraviolet (UV) radiations could stimulate rotundone production. The aim of this study was to investigate under field trial conditions the impact of grape exposure and UV treatments on rotundone in Vitis vinifera L. Tardif, an almost extinct grape variety from south-west France that can express particularly high rotundone levels. Four different treatments were compared in 2021 to a control treatment using a randomised complete block design with three replications per treatment. Grape exposure was manipulated through early or late defoliation. Leaf and laterals shoots were removed at Eichorn Lorenz growth stages 32 or 34 on the morning-sun side of the canopy. During grape maturation, UV radiations were either reduced by 99% by installing UV radiation-shielding sheets, or applied four times using the Boxilumix™ non thermal device (Asclepios Tech, Tournefeuille) with the aim of activating plant signalling pathway. Loggers displayed in solar radiation shields were used to assess the effect of such shielding sheets on air temperature within the bunch zone. The composition of grapes subjected to these treatments will be soon analysed for their rotundone content and basic classical laboratory analyses. Grapes will be harvested to elaborate wines under standardized small-scale vinification conditions (60kg) that will be assessed by a trained sensory panel.

Chemical and microbiological evaluation of Ribeiro wines (NW Spain)

Wine produced under Designation of Origin (DOP) Ribeiro, the oldest DOP in Galicia (NW Spain), are elaborated using local grape cultivars, grown at the valleys of Miño, Avia and Arnoia rivers. The landscape formed by slopes and terraces and the peculiar climate of continental character, softened by the proximity of Atlantic Ocean, make it an area of excellent aptitude for vine cultivation. In addition, small-scale farming and the use of traditional techniques for vineyard management provide a great diversity to Ribeiro wines. This study presents the evaluation of red and white wines (bottled or bulk wines) from DOP Ribeiro, produced between years 2018-2022.

Comportement de différents clones de Sauvignon blanc dans certains terroirs viticoles du Friuli-Venezia Giulia (Nord-Est de l’Italie)

The worldwide reputation of Sauvignon Blanc has led technicians to ask themselves various questions about the cultivation of this variety: choice of the most suitable localities, the most effective agronomic strategies and the most appropriate wine-growing techniques, to bring out its particular aroma.

EFFECT OF WHOLE BUNCH VINIFICATION ON THE ABUNDANCE OF A SWEETENING COMPOUND

In classic red wine-making process, grapes are usually destemmed between harvest and the filling of the vat. However, some winemakers choose to let all or a part of the stems in contact with the juice during vatting, this is called whole bunch vinification. For instance, this practice is traditionally used in some French wine regions, notably in Burgundy, Beaujolais and the Rhone Valley. The choice to keep this part of the grape is likely to affect the sensory properties of wine, as its gustatory perception1,2.