Sensory evaluation of grape berries: predictive power for sensory properties of Sauvignon blanc, Riesling and Pinot noir wines

Abstract

Sensory analysis of grape berries is a common tool to evaluate the degree of grape maturation and to make sound picking decisions. However, most of it is based on anecdotal knowledge and scientific studies relating berry and wine properties are rather limited [1]. 

Ten grapes of each variety (Sauvignon Blanc, Riesling, Pinot Noir) were picked weekly. Berries were dissected manually to obtain berries with intact peduncles. Using sucrose solutions of different densities, berries were separated into three density fractions of 1.070, 1.080, and 1.090. Three individual berries were assessed of each density group on each picking date. White and red wines were made from grapes picked concurrently with berry samples and were fermented in duplicates [2]. 

For Sauvignon Blanc 13 out of 21 visual, haptic, odor and taste attributes varied significantly among the three picking dates. Firmness and yellow color of the berries and brown color of the seeds and bitter berry skins yielded the largest F-ratios. Green notes in pulp and skin decreased during ripening. Variation of grape berry density yielded 14 significant attributes, including sweet and sour taste as well as fruity perception [2]. 

In a PCA the first PC was governed by ripe versus unripe attributes, while PC2 was dominated by presence versus absence of green odors in pulp and skin. Sensory evaluation revealed better grouping by density than grouping by picking date. 

Correlating berry and wine sensory brown seeds and sweet pulp correlated with increased peach and passionfruit notes in the wines. However, no correlation was found for green notes depicted in berries and green bell pepper nuances in the wines or fruity aspects in the berry and passion fruit / peach intensities in the wine. 

In conclusion, berry sensory yields a good characterization of the ripening process as well as technological grape properties, but is rather limited in the prediction of wine sensory properties. 

[1] Winter, E, Whiting, J., Rousseau, J. Berry Sensory Assessment, 2004, Winetitles, Adelaide, Australia 
[2] Nopora, J., Klink, S., Fischer, U. Reifeprüfung – Aussagekraft der Beerensensorik bei der Reifemessung, 2018, Der Deutsche Weinbau 17/18, pg. 26-30