 IVES 9 IVES Conference Series 9 From vineyard to bottle. Rationalizing grape compositional drivers of the expression of valpolicella aroma ‘terroir’

From vineyard to bottle. Rationalizing grape compositional drivers of the expression of valpolicella aroma ‘terroir’

Abstract

AIM: Valpolicella is a renowned Italian wine-producing region (Paronetto, 1981). Wines produced in its different sub-regions are anecdotally believed to be aromatically different, although there is no systematic study addressing the chemical bases of such diversity. Aroma is the product of a biochemical and technological series of steps (Kotseridis, et al., 1999), as well as one of the most important features in the expression of the geographic identity and sensory uniqueness of a wine. The aim of this study was to investigate the volatile chemical composition of wines obtained from grapes harvested in selected vineyards during three consecutive vintages, assess the existence of recurring patterns that could represent unique aroma chemical signatures and to identify key grape compositional features underling such aroma signature.

METHODS: Corvina and Corvinone grapes were harvested from five different vineyards located in two sub-regions within Valpolicella during three consecutive vintages. Winemaking was performed under standardized conditions. Free volatile compounds and glycosidic precursors were analysed with GC-MS analysis co. Sensory characteristics of the wines have been investigated through sorting tasks performed with semi-trained panel.

RESULTS: Application of multivariate data analysis techniques allowed to identify volatile chemical patterns representing the unique aroma chemical signature of the geographical origin of each wine regardless of vintages. The main drivers associated with these chemical signatures were terpenes (linalool, α-terpineol), norisoprenoids (vitispirane, TDN, TPB), and, unexpectedly some fermentation derived esters. Wines’ terpenes content was related with grapes terpenes pool. In particular variations in wine linalool content were strongly associated with the grape content of different linalool forms. Finally, in the case of esters, a strong correlation between grape content of yeast assimilable nitrogen (YAN) and wine ester content was observed, further broadening the boundaries of vineyard factors able to influence wine aroma. Patterns of odor similarities were observed during sensory evaluation, indicating a recurring association between geographical origin and occurrence of aroma compounds such as linear and cyclic terpenes, esters or norisoprenoids.

CONCLUSIONS:

This study provides evidence for the existence of volatile chemical signatures that are representative of geographical origin. Identification of grapes compositional characteristics related to the main drivers of wines chemical signature provides clues to support producers in identifying and managing appropriate vineyard and/or winemaking practices, in the quest of producing wines expressing their sense of place and ‘terroir’

DOI:

Publication date: September 10, 2021

Issue: Macrowine 2021

Type: Article

Authors

Giovanni Luzzini

University of Verona,Davide SLAGHENAUFI, University of Verona Maurizio, UGLIANO, University of Verona Jessica, SAMANIEGO-SOLIS, University of Verona Riccardo TEDESCHI, Azienda Agricola F.lli Tedeschi

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Keywords

chemical signature of geographical identity, red wine aroma, valpolicella, terroir, crus

Citation

The impact of Saccharomyces yeasts on wine varietal aroma, wine aging and wine longevity

The objective of the present work is to assess yeast effects on the development of wine varietal aroma throughout aging and on wine longevity.

Three independent experiments were carried out; two fermenting semi-synthetic musts fortified with polyphenols and aroma precursors extracted from Tempranillo (1) or Albariño (2) grapes and with synthetic precursors of polyfunctional mercaptans (PFMs), and a third in which a must, mixture of 6 different grape varieties was used. In all cases, fermentations were carried out by different Saccharomyces cerevisiae strains and one S. kudriavzevii, and the obtained wines were further submitted to anoxic accelerated aging to reproduce bottle aging. The volatile profile of the wines was analyzed using several chromatographic procedures, in order to provide a comprehensive evaluation of wine aroma. Aroma compounds analyzed included fermentation volatile metabolites, grape-derived aroma compounds including PFMs, and Strecker aldehydes (SA).

Results revealed that the effects of yeast on wine aroma throughout its self-life extend along three main axes:

1. A direct or indirect action on primary varietal aroma and on its evolution during wine
aging.

2. The direct production of SA during fermentation and/or their delayed formation by producing the required reagents (amino acids + dicarbonyls) for Strecker degradation
during anoxic aging.

3. Producing acids (leucidic, branched acids) precursors to fruity esters. More specifically, and leaving aside the infrequent de novo formation, the action of the different strains of yeast on primary varietal aroma takes four different forms:

1.- Speeding the hydrolysis of aroma precursors, which leads to early aroma formation without changing the amount of aroma formed. In the case of labile molecules, such as linalool, the enhancement of young wine aroma implies a short-living wine. 2.- Metabolizing the aroma precursor, reducing the amounts of aroma formed, which can be of advantage for negative aroma compounds, such as TDN or guaiacol; 3.- Transforming grape components into aroma precursors, increasing the amounts of aroma formed, as for ethyl cinnamate, leucidic acid or vinylphenols; 4.- Forming reactive species such as vinylphenols able to destroy varietal polyfunctional mercaptans.

Overall, it can be concluded that the yeast carrying alcoholic fermentation not only influences fermentative wine aroma but also affects to the wine varietal aroma, to its evolution during aging and to the development of oxidative off-odors

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