From grape berries to wines: drought impacts on key secondary metabolites

Stefania Savoi,Silvia Carlin,Fulvio Mattivi,Jose Carlos Herrera,Enrico Peterlunger,Cesare Lotti,Barbara Bucchetti,Simone Diego Castellarin

doi:10.20870/oeno-one.2020.54.3.3093

Abstract

Aim. We aimed to study the impact of water deficit on the concentration of key flavour and phenolic secondary metabolites of wines.Methods and results. A drought-stress field trial was conducted on Vitis vinifera cv. Merlot and Tocai Friulano for two seasons. Fully irrigated (C) and deficit irrigated (D) grapes were microvinified and the resulting wines were analysed to determine the concentrations of anthocyanins, tannins, and free and glycosidically-bound Volatile Organic Compounds (VOCs). A descriptive sensory test was undertaken on the same wines. Water stressed grapes produced wines with higher concentrations of anthocyanins in Merlot and of free and glycosidically-bound monoterpenes in Tocai Friulano. Both cultivars displayed higher amounts of glycosidically-bound C13-norisoprenoids.Conclusions. Previously observed drought-induced compositional changes to the grapes were transfered to the wines, with an increase in polyphenols and VOCs. However, the timing and the duration of the water stress in the field only heavily impacted the final wine composition with major metabolic modification when the severe water deficit started early (at approximately 40 days after anthesis) and lasted over the entire season until harvest.Significance and impact of the study. This study highlights the positive role of a controlled water deficit on the composition of the wines in terms of secondary metabolites.

Highlights

Grape berry quality, and the value of the derived wines, is tightly linked to the accumulation of secondary metabolites, such as polyphenols and Volatile Organic Compounds (VOCs), which contribute to the final colour, taste, and aroma of a wine
In previous studies (Savoi et al, 2016, 2017), we evaluated the impact of water deficit on grape berry ripening and composition for two different wine grape varieties widely cultivated in northeastern Italy (Tocai Friulano and Merlot) using a transcriptomics and metabolomics approach
Two water treatments were applied to the vines during two consecutive seasons which mainly differed in rainfall distribution (Figure S1)

Summary

Introduction

The value of the derived wines, is tightly linked to the accumulation of secondary metabolites, such as polyphenols and Volatile Organic Compounds (VOCs), which contribute to the final colour, taste, and aroma of a wine. Condensed tannins are complex polymers of flavan-3-ols which are primarily synthesised in grape berry skins and seeds at preveraison. They have a role in the taste of wines (e.g., astringency, bitterness, mouthfeel, and body) and they contribute to colour stability by forming several adducts with anthocyanins (Oliveira et al, 2017). Previous studies have reported little or no modulation of flavan-3-ols and condensed tannins resulting from a water deficit (Castellarin et al, 2007; Hochberg et al, 2015; Savoi et al, 2016, 2017)

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Conclusion