Application of fluorescence spectroscopy with multivariate analysis for authentication of Shiraz wines from different regions

Les études d’impact du climat sur la vigne nécessite de descendre à des échelles très fines car les facteurs climatiques sont tributaires de la topographie, la végétation, les expositions … Dans le cadre du programme ANR-JC Terviclim, 22 capteurs ont été installés dans les vignobles des Coteaux du Layon afin de caractériser le climat particulier de ces terroirs. L’analyse des températures montre de fortes disparités entre les data loggers et pourtant situés parfois sur les mêmes parcelles ou sur des parcelles voisines. Les indices bioclimatiques tels les degrés jours sont également contrastés suivant la situation des capteurs sur les coteaux.

New Zealand viticulture has long been characterised by sustainable grape growing practices as promoted by Sustainable Winegrowing New Zealand (SWNZ) as well as by Organic Viticulture.

Aim: The aim of this work is educating people about soil variability, vine rootzone depth and readily available water holding capacity. The concept of terroir is readily discussed in the wine industry but many people involved are unable to describe a soil profile and interpret its limitations that impact on vine growth, fruit quality and wine produced. This paper discusses soil physical characteristics important to vine root growth and readily available water holding capacity (RAW).

In red wines the post-MLF SO2 addition is an essential event. It is also the case for the “mutage” during the elaboration of the “liquoreux”. At these moments SO2 plays an antimicrobial action and an antioxidant effect. But at current pH of wines, ensuring a powerful molecular SO2 has become very difficult. Recent work on Brettanomyces strains have also shown that some strains are resistant up to 1.2 mg / L of molecular SO2. It’s also the case of the some Saccharomuces or Zygosaccharomyces strains suitable to re-ferment “liquoreux” wines after the “mutage”.

The aim of this study was to evaluate the effects of different soil types on the chemical composition of Mediterranean red wines, through untargeted and targeted 1H-NMR metabolomics. One milliliter of raw wine was analyzed by means of a Bruker Avance II 400 spectrometer operating at 400.15 MHz. The spectra were recorded by applying the NOESYGPPS1D pulse sequency, to achieve water and ethanol signals suppression. No modification of the pH was performed to avoid any chemical alteration of the matrix. The generation of input variables for untargeted analysis was done via bucketing the spectra. The resulting dataset was preprocessed prior to perform unsupervised PCA, by means of MetaboAnalyst web-based tool suite. The identification of compounds for the targeted analysis was performed by comparison to pure compounds spectra by means of SMA plug-in of MNova 14.2.3 software. The dataset containing the concentrations (%) of identified compounds was subjected to one-way analysis of variance (ANOVA) to highlight significant differences among the wines. The untargeted analysis, carried out through the PCA, revealed a clear differentiation among the wines. The fragments of the spectra contributing mostly to the separation were attributed to flavonoids, aroma compounds and amino acids. The targeted analysis leaded to the identification of 68 compounds, whose concentrations were significant different among the wines. The results were related to soils physical-chemical analysis and showed that: 1) high concentrations of flavan-3-ols and flavonols are correlated with high clay content in soils; 2) high concentrations of anthocyanins, amino acids, and aroma compounds are correlated with neutral and moderately alkaline soil pH; 3) low concentrations of flavonoids and aroma compounds are correlated with high soil organic matter content and acidic pH. The 1H-NMR metabolomic analysis proved to be an excellent tool to discriminate between wines originating from grapes grown on different soil types and revealed that soils in the Mediterranean area exert a strong impact on the chemical composition of the wines.