Evaluation de la variabilité du vignoble par échantillonnage ciblé de raisins

Matthias FRIEDEL, Magali LAFONTAINE, Vincenzo SORRENTINO, Manfred STOLL
*Corresponding author*: M. FRIEDEL -  Email : matthias.friedel@hs-gm-de

Abstract

Variability of grape quality traits is encountered in vineyards between individual vines, between clusters within a single vine, and between berries of single bunches. While precision viticulture addresses systematic geologic and microclimatic variance within a vineyard, the within-vine and within-bunch variability are inaccessible to targeted management or selective harvesting. Recently, a new generation of berry sorting systems has emerged on the market, which allows single berry sorting by berry size, shape or reflection in several parts of the electromagnetic spectrum. However, the implications of berry size and optical properties for wine quality need to be understood in order to conduct targeted berry sorting. The aim of this project was to determine to which extent variability of berry quality traits exists on within-vineyard, within-vine and within-bunch level and to determine the covariance of berry optical properties with berry quality traits and finally to determine berry size and color effects on wine quality of Riesling (Vitis vinifera L.). Therefore, variance of grape quality parameters within vineyards, individual vines and bunches has been analyzed for sugar, organic acids, amino acids and skin phenolics (only within-bunch and within-vine variability) in the seasons 2010-2013. Results showed that within-vine and within-bunch variability exist on similar levels as within-vineyard variability. While organic acids, amino acids and phenolics correlated well with berry optical properties (VIS-Spectrum and Fluorescence) or berry size, others, especially sugars, showed little correlation. Results of a trial conducted in 2013 showed significant implications of berry size and color on the organic acid, terpenoid and norisoprenoid composition of wines obtained by micro-fermentation.

Keywords : Aroma compounds, Berry optical properties, Berry size, Targeted berry sorting, Variability

Résumé

La variabilité des paramètres de qualité du raisin, des vignes individuelles et de rangs a été analysée pour les sucres, les acides organiques et aminés, les composes phénoliques des pellicules dans la période 2010-2013. Les résultats ont montré que la variabilité entre vignes et entre rangs existe à des niveaux semblables à celle de la variabilité dans le vignoble. Alors que les acides organiques et aminés ainsi que les composés phénoliques ont bien été correlés avec les proprietés optiques de la baie (Le VIS-SPECTRE et la Fluorescence) ou la taille de la baie, d’autres, particulièrement les sucres, ont montré peu de correlation. Les résultats d’un essai conduit en 2013 ont montré les implications significatives de la taille de la baie sur la couleur, les acides organiques, les terpènes et les norisoprénoïdes des vins obtenus en micro-fermentation.

Mots-clés : Composés aromatiques, Propriétés optiques du raisin, Taille de la baie, Echantillonnage ciblé de raisins, Variabilité